The Breckenridge/Summitt Cty area is not geared well to young children. You have Gold Mine tours, an Alpine slide, boats, etc. in Breckenridge area but 2 and 4 is too young. There are bike rentals and trails.

You have the Children's Museum in Denver that would appeal to the kids and, of course, the zoo. The the open carriage train ride from Georgetown would appeal to the four year old.

Tiny town in the foothills of Denver would make for a good half day trip from Denver as would the train museum in Golden. Garden of the God is very scenic but that is about it. The cog railroad to Pikes Peak could be fun but bring good jackets.

The Children's Museum may be a possibility but be aware it is just an expensive play room. I consider it a complete ripoff. The zoo is very good, and the Museum of Natural History could be interesting to them. In Morrison, just on the outskirts of Denver there is a little dinosaur museum that they might enjoy. there is also Dinosaur Ridge but they may be a little too little.
Eat at Casa Bonita--Mexican restaurant with passable food and a cute exhibit and show for kids. Also the White Fence Farm--goodish family style food and fun things for little children.
Denver folks, is the Aquarium still open?

Yes

Colorado Railroad Museum in Golden is 2 and 4 year old boy heaven. It has real rail cars to explore.

In Vail, you can ride the gondola in the summer. Vail has a sizable pedestrian area which is kid friendly. There's minigolf and and a playground at the base of Vail. Breck probably has a playground too, and a chair lift ride in the summer.

Any Breckinridge restaurant is kid friendly. if you go to the Breckinridge ski resort website, you'll find links for summer activities in Breckinridge and a list of restaurants. There is a great breakfast place called the Blue Moose. For other meals, you'll find the standard ski resort spots with burgers, steak, mexican, pizza, etc. Keystone has a fondue place at the top of the mountain. Not sure if it's open in the summer. Vail and Beaver Creek have many more fine dining options. if your kids can remain seated through dinner, you can take them anywhere at Vail/BC. You can also go casually dressed.

The little town of Minturn has a mexican restaurant with a train that runs around the ceiling. Also, the Minturn Country Club is a totally casual, hole in the wall place where you cook your own steak. When my boys were your guys' age, it was their favorite restaurant. (We've been to the Vail/Breck more than a dozen times in the winter and summer over the last ten years.)

Fmpden's post is good and accurate. Gretchen's being a bit cranky about the Kid's Museum. I wouldn't go out of my way to go to Casa Bonita but my kids were oddly fascinated by it. The food is chain restaurant quality.

Fmpden, do you know which exit on 70 has the buffalo area? My boys loved stopping to look at the buffalo.

Casa Bonita is totally for the kids. I'm thrilled we've aged out. It is my firm opinion about the Children's "museum". Have you been? There's little to no "museum"--it is a playhouse. And expensive.
The Aquarium would be really good. Glad it has survived.
Casa has a diving show.

There's a big difference between a 2-year-old and a 4-year-old. I think all three of my kids would have liked the Country Boy mine when they were 4, but not when they were 2. They also would have liked the panning for gold afterward.

They would like the cogtrain up to Pike's Peak. We went to Garden of the Gods and it was probably a little too late in the day and pretty hot out. My daughter actually liked the little nature center as much as anything.

I don't. I have lived here too long. I just know where it is. It is reasonably well marked. Those buffaloes are a part of the Denver park system. There is a firehouse museum in downtown Denver. Have not visited so have no recommendation regarding it. Just remember, they may enjoy the butterfly house - goggle it. About half way between Boulder and Denver but very kid oriented.

Loving this advice! My husband will especially enjoy the firehouse museum as he is a career firefighter. We'd definitely like to do a train ride in the mountains.

The butterfly pavilion is REALLY neat--other insects and creepy crawlies too--halfway between Denver and Boulder in Westminster.
Another thing they might find interesting just for aroma is a visit to the Celestial Seasonings Factory in Boulder.

The Butterfly Pavilion is in Westminster right off US 36 at Church Range Rd. US 36 is the main highway between Denver and Boulder and starts at I-25. Definitely good for young children and relatively inexpensive if I remember correctly:
http://www.butterflies.org/


Train ride - Georgetown Loop railroad - we did this the first fall we moved here 10 years ago when my kids were 3 and 5 and e all enjoyed it - not your average train ride.
http://georgetownlooprr.com/
Georgetown is a cute town with a small town with local shops along the few main streets - ice cream, candy and a few restaurants.

The Butterfly Pavilion is in Westminster right off US 36 at Church Range Rd. US 36 is the main highway between Denver and Boulder and starts at I-25. Definitely good for young children and relatively inexpensive if I remember correctly:
http://www.butterflies.org/


Train ride - Georgetown Loop railroad - we did this the first fall we moved here 10 years ago when my kids were 3 and 5 and e all enjoyed it - not your average train ride.
http://georgetownlooprr.com/
Georgetown is a cute town with a small town with local shops along the few main streets - ice cream, candy and a few restaurants.

Breckenridge actually has a children's museum called the Mountain Top Museum with fun, hands-on activities for kiddos even as young as two. It's open daily and very reasonable. You should also check out the Breckenridge Recreation Center. The fantastic pool has a spacious kid's area with fountains and mini-slide for younger kids. If you have time during the week, Family Gym time is also available usually twice a week with a small bouncy house, mats, tunnels, and other toddler-friendly equipment.

Of course, get the family out on the many hiking trails easily accessible right from town. Try the Burro Trail from the Beaver Run Resort.
I agree

Thanks so much BreckRec! Great ideas for Breckenridge activities with little ones.