Congrats!
You're going to get advice of all kinds on this subject. I can only share our experiences.

We have a now 3.5 yr old. She was born while we were living abroad. At last count, she has logged over 40 trips, including Mexico, the States, and the UK.

We have found that our scheduling and planning needed to be loosened quite a bit. She has taught us to slow down, and find entertainment in spontaneous moments. She has been a tremendous ice-breaker, there's something about a small child that warms up complete strangers.

Things WILL change. You can't travel as lightly, or as last-minute. Lay-overs need to be a little longer. Hotels are chosen for amenities like the ability to provide a safe sleep area for little one. What helped us was remembering that every country, every destination, has children. Go. Enjoy.

We found that it was helpful to stay in an apartment so we could have separate sleeping areas and a kitchen.

We also realized that the more we could keep to the children's home eating and sleeping schedule, the better time we all had.

BE FLEXIBLE. Don't overplan, and understand that every child is different. You don't mention how old your oldest is, but I can tell you my experiences traveling with children. My mom, sister and I took our girls to Europe when my niece was 4 and my daughter was 12. We WAY overplanned and were all exhausted. My niece and daughter were well behaved but got fidgety if we spent too much time in museums or tried to go too long between meals (remember that your little one might be hungry/thirsty even if YOU are not). My nephew would be a nightmare to take on a trip like that. Plan things your child would enjoy. If your child is active and/or has a short attention span (my nephew) plan more activities where he can run around and fewer activities confined to a car, bus or train. Also remember that what is awesome to you may be ho-hum to him. My parents took my daughter to New York City and London when she was 8. I thought she would be impressed by the skyscrapers in NYC and by the crown jewels in London. The highlights for her~feeding the horse who drew their carragie through Central Park and getting a hot dog from a street vendor in NYC, and the "biscuits" the maid left in the hotel.

tenthumbs is so right - as long as we can find ducks or pigeons to feed, our DD is happy as a clam. It's the little things.

We always had great times on our trips. Of course its a bit more trickier to travel with kids, but its possible. Most times we travel by car or train. I have a little helpful article for you: http://www.best-travel-site.com/travelguide/keeping-the-kids-happy-during-long-road-trips/
Maybe you will find some tips. And tell your husband that he has not to be afraid or something else. In my family it worked. So why should not in yours?!
Congrats to your first born!

We have 4. Did not start taking them overseas until the last 2-3 years. Have now had some incredible travel experiences with them...almost nothing beats the pure joy of watching the 4 kids interact with each other in new ways (because there's no-one else to play with and even better interacting with kids with whom they have no common language. Beats every other cultural experience I've had...pure delight and pride.. Another thought...in many Asian countries their love of children and the cheap prices may mean you get more of a break than you ever would at home!!

Travel with your kids! Mine got on planes at 8 weeks and now they are thriving, empathetic, daring, culturally aware girls who are now 4 1/2, 8 1/2, and 10. It was crossing the Namibian desert last June that they were looking on a map and chose our next destination to Cambodia, Vietnam and Laos! Now we are planning this trip together.

When they were little I did pack lots of stuff as I wanted to ensure that I had what I needed and they needed to be comfortable. When I could, I fed-exed stuff in advance. Case in point when we celebrated XMAS on a safari in South Africa and all of santa's presents made it under a beautiful XMAS tree in the bush.

Someone pointed out that your children will be different and so you have to compromise and go with the flow. This is so true. One of my girls has more of a travel bug than me and is a major foodie. Another likes to travel but is ready to come home after 2 weeks and only eats pasta and chicken fingers. So my dream of living in Paris for two months one summer will have to wait and I stay in locations that can feed my child! But she was never so happy as she was when we spent her Spring break week in Paris.

Last couple of things...get your locations where seasons matter out of the way before your first child starts school. There are lots of places that we want to go but the weather is wrong when we have breaks. Also, don't hesitate to call a place that says they don't allow small children. When I do and explain about the number of countries my kids have visited, they often make exceptions. And the younger you travel with your kids the faster they will think it is just a normal fact of life and will be as easy as pie. My kids, even the 4 1/2 year old pack their own backpacks. All they want to know is how long is the flight so they can prepare. They can knock out an 18 hour flight with the best of them!

Congrats on your pregnancy. Here's to new life and the joy of travel!

>get your locations where seasons matter out of the way before your first child starts school.<

I often took my daughter out of school to travel. A few of her teachers were miffed at the "extra" work it created for them, but many of them encouraged travel. My ex was a low seniority police officer when our kids were little and couldn't get summer vacations or time off during school breaks, so we scheduled family vacations when he could get time off. My daughter missed school up until her senior year in high school and had no problem making up the work. I have also kept the journals the teachers asked her to keep and enjoy looking back at them.

It's very helpful hearing all of your thoughts, thank you! I love hearing your stories about Christmas in South Africa and the small joys of New York City. My husband and I are both teachers ourselves, so we are already accustomed to seasonal travel, even without kids. I'm now 25 weeks along, so the reality of the future is starting to sink in.