Hi! I live about 20 miles from OOB. The beach is beautiful, but can get quite crowded in the summer, especially around the pier area. Stake out your spot early!
If you're looking for junky type food, there is a ton of it on the main street and in Palace Playland. You have to eat some Pier Fries- they are the best!
The Clambake Restauant is down the road in Pine Point. It is a big, informal place and the food is very good. The Captain's Galley is a mile or so from the main street, and also has very good food. Both places have gift shops that carry Maine type items that are nicer than the things you might find in downtown OOB shops. The Captain Galley's gift shop is small, but the one in the Clambake and especially the one right next to the Clambake, are quite large.
Also, in Saco, the next town over, you'll find Funtown/Splashtown USA, a big amusement/water park. If you have kids, you could probably spend a good portion of a day there. They have lots of rides, food, and live entertainment.
Any other questions, just ask! Hope you have a good vacation! So far we've had pretty good weather this summer, not much humidity or high heat.