NATHAN is loving this! He'll go swimming every chance he gets, and otherwise is a lazy beach bum for the entire week. It's likely he sleeps outside in a hammock a few times, and otherwise has some books with him to read while he's outside. Pretty chill.
GODRIC has never seen a beach set-up quite like this before, though he has seen some pretty nice beaches. I have the hilarious mental image of him dressed in casual modern clothing just hanging out and wading around in the water, so this happens. He'll join in any sports or whatever people get up to, and definitely enjoys some hammock time. Not even 10th-century adventurers can turn down a beach paradise...
GEORGE is all about outdoor activities! Bonfires, water games, volleyball (with Emmeline!?), barbecues, you name it, he's on it. By the end of this week he's going to be awfully sunburnt, but he doesn't really care right now. Somebody please remind him to use sun-screen charms/lotion/something/a hat?
JASPER can't really resist the beachy set-up either. He'll probably do his usual thing and keep mostly to himself, though certain people might be able to drag him out of his shell and get him to participate in group activities. If Vogg comes to the beach, he'll want to spend time with him, because Vogg is his new daddy.
WENDELIN will stare jaw-dropped at anyone, male or female, if they wear swimsuits. This sort of thing is, like, WHAT?! She won't dress immodestly, and someone will have to poke her to be social/outgoing as well, but eventually she'll relax enough to have a good time, even if, like Jasper, she keeps to herself.
THEODORE stays inside most of the time, because large crowds make him uncomfortable, but at night once it's quieter and most people have gone home, you'll see him slinking around outside and lying down in the hammocks. The ocean is soothing for his mind/spirit and it helps him relax enough to sleep.