Jasper and/or Banff national parks, Alberta, Canada. The national parks are cheap to camp in but there are also plenty of hotels etc. in all price ranges and levels of pampering. There is a ton of gorgeous natural stuff to take in that is basically all for free- walking/hiking trails, parks, etc. And there are hot springs and tours and stuff you can pay to do. It is totally family friendly and the two cities are a 3 hour drive from each other through some of the most gorgeous mountain scenery you have ever seen. Plus in the middle is the Columbia Ice Field which is incredible- you can take a tour on the glacier itself. Banff is more touristy than Jasper.
Also Vancouver, BC and Vancouver Island, BC. Incredibly beautiful places with tons to see and do.
Give Canada a try!
Depends on where you live. I used to live in South Florida and we love Captiva Island. I think it is very old florida! It isn't comercialized like so many of the other towns. It is small and quaint, with beautiful beaches and great restaurants! You can kayak thru the mangroves and bike all over the island too. google it! I would suggest VRBO.com to find a beach house to rent! You and your kids will love it!
We absolutely loved Hilton Head Island. We rented a condo for a week through VRBO.com. (Vacation Rentals By Owner) and it was really reasonable (we went in June). My daughter absolutely loved the beach (the beaches are phenomenal!) Before we actually made it to the island, we bought groceries at a Super Walmart--a week's worth (groceries are more $$$ when you get on the island). The condo had a full kitchen and we ate most of our meals in, which saved us a lot. We drove there too (live in Chicago). Hilton Head can be expensive (if you do a resort, or if you golf), but our condo was just steps from the beach, had a pool, and was a great destination for a toddler & family. For the last few vacations, we've gone through VRBO for rentals and have had great success with them. We've found some fabulous places to stay for a fraction of what you'd pay at a resort. Our condo even had a great view, so we didn't want to go anywhere else for meals!