We love the Outer banks.
This past Summer we spent over 2 weeks in Portland, OR area. We stayed in Portland the majority of the time. Still is more there that we did not get to. The major draw to Portland is it is about 2 hours from the beach and 2 hours from the mountains. We did it all. Love the beach! It was cold and we needed to buy coats. We loved the break from the heat!
Cannon Beach was our ultimate favorite place.

Haystack Rock has sea stars, seas cucumbers and so much more to see and investigate. You can rent beach bikes that are similar to trikes. Looks like so much fun. You are allowed to have bonfires on the beach.
Mt Hood was beautiful as well. We also spent a long weekend in Seattle, WA.
We would love to have at least a week to spend at the beach. A little further south they have dune buggy rentals and rides too!
http://www.cannonbeach.org/
Branson, MO is very affordable. Water parks, water sports, lots of shows, great food, amusement parks and more. We go there alot because it is driving distance for us and my parents live close by there. They now have their own airport as well.