@sfombom,
Take a beach umbrella. If you don't have one, take a couple of folding beach chairs and a blanket to make some shade for them to huddle under when not in the water. Have them wear t-shirts while in the water to help limit the sunburns.
Take a lot of drinking water to keep them hydrated.
If you go, go before noon to avoid the hottest time of day when the sun's rays do the most damage.