At the end of last summer I bought a mistral n-trance and 2.5m rig for my girls. We only had chance to get out on it once and on that occasion, their mothercare swim floats (the ones with the removable foam inserts) were fine. They've now outgrown them though and they're very excited to get back on the water again this summer but I don't think their armbands are quite going to cut the mustard.

What should I be looking for..? Will a buoyancy aid be OK or should I be going for a more full on life jacket? They love being in the water in the swimming pool and are really confident with their arm bands on but I can't help thinking a bit of float support behind the head would be a good thing. They'll be four y/o in a couple of weeks time.

Advice appreciated, please.