I might be able to help with a couple of your questions. As far as the guides at Hanging Bridges - we have been there twice. The first time we went directly to the window, didn't have a tour booked and asked for a guided tour. They got us a guide. This was in May though. Since you are going over the Holiday's and hope to use one of their guides, I would book one directly. If not through Hanging Bridges, then with a company that does offer guided tours. The walk will be much more meaningful if you have a guide to help spot wildlife as well as to explain what you are seeing.

I would consult your husband's doctor regarding activities when it comes to his heart condition. Not only regarding zip lining but the hiking as well. It's not all strenuous, but there are inclines that may be difficult.

That being said, we traveled to Costa Rica with my parents about two years ago. My dad had recently had some knee problems and back issues that he had surgery for and he has moderate asthma. He was able to hike moderate trails at his pace. He brought lightweight walking sticks, I believe from LL Bean. They helped him quite a bit. My mom also used a set. There is a lot of uneven terrain and they were great for balance.

My dad went zip lining at Sky Trek (he was 66 at the time of the trip I think) and loved it. The zip lining wasn't strenuous, but it is definitely exhilarating! My mom had no interest in doing it. Now my husband - even with a good heart - at age 43, he probably would have had heart issues doing it! So that is more a personal thing I think. And there are more moderate zip lines that aren't so high, fast or long.

Find out if it's ok to be in the Hot Springs at Tabacon are ok with the hot condition as well. Some are very hot.

My parents loved Costa Rica and would enjoy a trip back! Have a great time!

Shell offers good advice as always. We've done the Hanging Bridges both with and without a guide. The first time we did it we only saw ants, so the next time we went back we hired a guide through Desafio, and he was wonderful. We saw a toucan, howler monkeys, a beautiful green honeycreeper, and some other cool things like plants and insects. I didn't see guides for hire when we went, but we were there at a quiet time. We've used Zender Chacon from Sunset Tours for other guided hikes and trips, and he's also amazing. Either of those two places could give you someone great.

La Fortuna waterfall is a lot of steps. It's not difficult going down, but coming back up a lot of people stop to catch their breath. If you're okay with lots of steps, it would be fine. I did it with a sprained ankle because I'm stubborn and was determined to go - ha, ha. It's beautiful. I'm very glad we did it. If you decide the steps are too much for you, there is an observation deck so you don't have to go all the way down. If you do go, there's little steps off to the left that lead down to a crystal clear river - very neat spot.

We've never done a twilight float trip. I'd be more inclined to do the Penas Blancas float or the Cano Negro tour - both during the day. You're more likely to see wildlife that way.

I wouldn't recommend ziplining for anyone with a heart condition, but like Shell said I'd check with your doctor. At Sky Trek, you travel at 55 mph and are 600 feet in the air - it's fast with long lines.

If you're doing the Hanging Bridges, I'd skip the bird walk at the Lost Iguana unless it's free. They are right next door to each other, and I don't think you'd see much that's different.

Proyecto Asis and Tabacon are both great - you'll enjoy those!

I would trust the Lost Iguana staff to arrange the Hanging Bridges stuff; they also give a (good) discounted price. You can enjoy the grounds (there's a self-guided hike) of Lost Iguana on your own, too.
I think the walk to the waterfall is probably not a great idea, given your description.
The zip line was a "piece of cake" according to my DH (well into his 60s); I rode the tram up and down, while he zipped, and walked through the butterfly garden at the bottom, and enjoyed a glass of wine while waiting for the zippers. (My objection to the zip is mostly price and disturbing the wildlife and nature; but I am all alone on my superior cloud; didn't stop me from riding the tram to the zip!

Francisco is the guide we used through Desafio if you want another rec. He's excellent, and really enthusiastic. For everything he showed us he would say, "Ah, this is something special..."

I had kind of a crazy experience on our zip. I was going so fast that it was hard to stop the first time, and I got huge bruises on my legs from the harness. It just jerked me really hard. The people on our tour told me they though I would shoot right off the end! It didn't really hurt so much as it was really jarring. I think it was just that it was a different braking system than I had used before, and the guides said they'd wiggle the line when it was time to stop, but they waited kind of late, or I waited kind of late. I'm still glad I did it, but also glad I don't have a heart condition.

sylva, I'm on the same cloud; I worry about there be too many humans zipping through the forests ... though I suppose we are, after all, just big monkeys. Well, some of us are... ! I've gone on tours, to Vernado Cave for example, that were likely worse for the animals and the environment.

My co-worker just returned with a shoulder injury from zip-lining - yes, being jarred. She's pretty young, with no heart condition.

Cano Negro trip would be a good idea....usually many birds and you will see local countryside. Hanging Bridges will be just a taste of what you will experience at Bosque del Cabo!!

Great info amigos y amigas. We'll skip the zip and bird tour given at fee from Lost Iguana. I'll check on Cano Negro & Penas Blancas with the companies mentioned. I'm wondering if my husband will get bored floating all day and seeing a monkey or two; he's set a high bar with our trips to Botswana and Zambia.
Any intel about what to wear at night in Arenal area? Does it get cold enough that I need a fleece jacket?