Must see's on the way- suggestions
Stockyards - Fort Worth
Palo Duro Canyon and the outdoor musical TEXAS in the canyon.Amarillo
Pikes Peak and Manitou Springs. Take business 24 from downtown to Manitou Springs. Colorado Springs.
Downtown Denver shopping center.
Estes Park and Rocky Mountain National Park. North of Denver
Blackhawk is just north of I-70 on the way to Breckinridge. Gambling with Casino's. Ameristar casino has 35 story hotel there with a roof top swimming pool and spa. Kids everywhere.
4 star with rooms half the price as other area's. The highway from Blackhawk to Boulder breathtaking.

Thank you very much DALEB. I will definitely look into your suggestions.

DALEB, looks like some great recommendations. Thanks!

On the way, you might check out Carlsbad Caverns and White Sands. While I've not been there myself, know several people that have and highly recommend them.

In Colorado, in addition to the suggestions you have and depending on interests:
Rockies game at Coors field
Garden of the Gods in Colorado Springs - free local park with numerous hiking trails and beautiful rock formations
Air Force Academy in Colorado Springs

In the mountains, take a horseback ride and see the views from a different perspective.
Rent bikes and if ambitious, take one of the ski gondolas to the top and ride down.
Hike a 14'er - there are 50+ in Colorado, some much easier than others - I hear Mount Evans is one that is doable as you can drive fairly high up before completing the hike.
Drive Trail Ridge rd in Rocky Mountain National Park - stop along the way for the beautiful views, check out trails, picnic, etc.

Boulder - Pearl St mall on a weekend - pedestrian mall with buskers usually out entertaining for tips. Numerous restaurants and cafes along it.

Have a great trip!

"Downtown Denver shopping center.".

I think you probably meant Cherry Creek shopping area, in particular the shops and restaurants in Cherry Creek North. CC mall is a nice upscale mall, too.

Downtown shopping is nothing to write home about, unfortunately. Restaurants and bars, yes. Shops, not so much, unless you enjoy high-end artsy boutiques on Larimer Square.

glynn1117 - You and your family are going to love that area of Colorado. Breckenridge is one of our favorite places in both winter and summer with so many fun things to do. We too are from the Houston area and just recently purchased a home outside of Breckenridge that we rent when we are not using it. Not sure if you have your accomodations yet but if you are still needing a place to stay you should take a look at our house - http://www.vrbo.com/43118 Have a fun trip with your family!

That house is oceanfront, North Carolina.

Aren't there kind of nice stores in LoDo any more. I was never particularly fond of the 16th Street mall, but youngsters might find stuff there. But Houston is no slouch for shopping so they may not "need" shopping.
I guess the poster above meant to post their new Breck place.
I hope you'll go to RMNP for at least a day.