Need a vacation spot for my family, no amusement parks!!?

I live in Houston, TX and want to drive my family to a great vacation spot. I have 1 year old twins, a 16 year old son who loves the outdoors and my husband and I. We will be traveling in an RV loaded with toys and gear for the babies I am sure. The guys like fresh water fishing. We also like bike riding, hiking and generally poking around new places. I am just hoping to have fun on vacation with 2 toddlers! We need to go to Connecticut for business in July, but my husband thinks it would take to long to drive and eat into to man of our days off. We are anticipating lots of stops!! Any ideas? We have about 3 weeks to spend on this vacation.