L.C.
Hi Meg,
We are currently stationed in DE and we love it here. School is back in so it shouldn't be as crowded as it was over the summer. We have only been to Rehoboth so far but we really loved it. The boardwalk is nice with lots of little restaurants and shops. The beach is lovely and if you get there by 10 AM you should be able to get a nice spot on the beach. Parking is $4 for every three hours and can only be paid with coins or a debit card, so for convenience have change ready.
This is totally non-beach related but also in Rehoboth they have a pretty kickin' outlet mall with a carter's and osh-kosh and so many other stores it's like Christmas for shoppers.
If you have any other questions feel free to PM me.
Hope this helps,
L.