We always bring the kids life jackets from home. (5yo, 8yo, 10yo) They are used to them and comfortable in them. We also bring snorkel equipment. A 90L Duffel holds all of it and then some. They dry very quickly so I wouldnt worry about bringing two of them. We have never had a problem. We did have problems with chafe, make sure to bring plenty of rash guards.

We dont use the straw hats, the kids are always wearing sun hoodies. So much better.