Best cheapie for teenagers is Garner State Park between Con Can and Leakey. Dance every night, spring-fed Frio River (think Country of 1100 Springs), mountain climbing (on a small scale), crystal caves, ice cave. The park cabins, shelters, and campsites are always sold out, but there are dozens of nice places around. I've been going there since 1951 I climbed the face of "Old Baldy" in 1959.
I also like Arkansas. Crater of Diamonds State Park near Murphresboro is great. North America's only diamond mine. You can rent the tools and you keep what you find. People have found diamonds every time we have been there. We found a big chunk of amethyst, some garnets, and lots of other gemstones.
Venavou Rocks in Wyoming are great. You can get affordable hotels, close by. You fly into CO, then take a beautiful 3 hour drive to Cheyenne, WY. It is a fun time, and too hot at this time of year.
Rocky Mt State Park in CO is great too. Don't stay in Estes, they are packed. Stay on the other side, nice condos, and way less crowded. Lots of snow at the top and this early some of the roads are still not open.
Pasadena, TX. You never know what is going to happen. See the nightly shimmering towers that make the chemicals of the world. Breath-in all your scented man-made minerals. Fish for the rare 3-eyed nuclear fish. Visit pubs that are only written about in police reports. Be the first to discover the strawberry fields that have yet to be seen on Strawberry Rd. after going to the Strawberry Festival (which is ironically on Red Bluff / May 18 - 20 - note the irony of "Red Bluff")