Kathy & Leo:
You will see ponies!! They will make good use of your awning for shade. I remember one trip there when I was younger there was a VW van camper next to us and the side door (that had a canopy attached to it) was left open, three ponies were standing under the canopy with thier heads very happily inside the van!!
You will need some protection from the Green Headed Flies and Mosquitoes, if you have a screen room I would strongly recommend you bring it. Shade is hard to come by, the flies fly in squadrons and have a mean bite. Depending on the wind (lack of any or blowing from the west off the bay) will bring out the bugs in force. An Ocean breeze will usually keep them at bay. Also, be prepared to anchor things (screen rooms, awning straps, etc.) in sand, regular anchors (standard tent pegs, corkscrews, etc.) are not going to hold.
If you think you would like to do some of the four wheeling mentioned, check the National Parks website for equipment you'll need. There is a permit required and quite a bit of stuff required (jack, shovel, jackboards, etc.)
This site will give you some idea of the activities available in the area (might help convince that 16yo G/S he'll be ok)
We also stay at Frontiertown mainly because mdfiregal wants full hookups! It's a real fun area. The town of Berlin is not far away if you like Antiques and such. BTW...Berlin has "stood in" as the fictional town of Hale, MD in the Runaway Bride
and the town of Treegap in Tuck Everlasting.
The area took a beating from the "Noreaster" that hit this past week, lots of erosion and flooding, but it should be back to "normal" soon.