Hello, my family wants to travel to Colorado. We have never been and are very overwhelmed on what we could do there. We are a family of four, with a 15 year old boy and an 12 year old girl. We are from the New Jersey/ Philadelphia area. We would like to see the nature Colorado provides, do some fun things like white water raft, while also staying at a resort-like hotel, etc. We aren't too knowledgeable of Colorado, but know that we want to go there in the summertime when the weather is in the higher temperatures. Any advice, must-do's, or helpful itineraries is greatly appreciated. Thank you in advance!

You can fly from Philadelphia to Colorado Springs. The airport there will be easier to negotiate than Denver's. Drive up majestic Pikes Peak and take a hike when on top (Timed-entry reservation system). Wander through the colorful rock formations at Garden of the Gods; go through Cave of the Winds; view the amazing Seven Falls; ride the Pikes Peak Cog Railway up Pike’s Peak (reservations suggested); wander around Manitou Springs eating saltwater taffy exploring art galleries and the historic Cliff House hotel. Hike the Catamount Falls Trail near Green Mountain Falls. Check out the Rocky Mt. Dinosaur Resource Center in Woodland Park. Eat Colorado trout down in the Rabbit Hole with its whimsical Alice in Wonderland décor or eat buffalo at a chuck wagon diner.

Two hours west of Col Spgs is Buena Vista where you can go whitewater-rafting on the Ark River. Spend the night in BV or Salida. You can rent bikes and ride on the old Midland Railroad right-of-way through four old railroad tunnels on Chaffee Co Rd 371, north of BV.

Start by visiting the public library and taking out a guidebook like Fodor's from the library to help with your planning. If you are an AAA member you can get a free road map. Most of their state guidebooks are now only available as digital editions but still helpful for research.

After whitewater-rafting you could go to Crested Butte. “Authentic, open and free of crowds, Crested Butte is a quaint 1880s mining town, a Registered National Historic District — and the celebrated wildflower capital of Colorado.” It is also a mountain biking capital with hundreds of miles of mt. biking trails nearby. It features rows of pastel Victorian storefronts which house boutique shops and restaurants. Crested Butte's Creative District encompasses the Center for the Arts, and 16 artist-owned studios and galleries. It is a major ski resort in the winter, during the rest of the year there are lots of outdoor activities such as hiking, kayaking, and horseback-riding.

PrairieHiker1 has given you some great suggestions for my home state. Just be aware that Crested Butte and much of CO is far from free of crowds these days. You'll want to book your lodgings well in advance.

You might also take a look at Durango and Ouray, a beautiful part of the state.

https://www.durango.org/

https://www.visitouray.com/

"We would like to see the nature Colorado provides, do some fun things like white water raft, while also staying at a resort-like hotel, etc"

Take a look at Devils Thumb Ranch, in Grand County. It's really nice. They have access to all the outdoor activities you want, plus a spa, a pool, great food, etc.
It's pricey, but worth it, You could visit during shoulder season.
Your kids could find things to do on their own.
https://www.devilsthumbranch.com/find-your-room/
Lots of different types of lodging-- rooms, suites, cabins, etc.

You might not need a car, if you don't want to drive there. Amtrak goes to Fraser, CO, and the Ranch will pick you up.

No one has mentioned Mesa Verde which should be a highlight of any trip to southern Colorado:


or the Durango to Silverton RR trip:

Thank You all for such great advice!

Great Sand Dunes NP is I think a Colorado highlight for teens and pre-teens, but to fully enjoy a person would have to camp there.