A chum would like to bring his tiny baby on board for a day sail and has asked if I can arrange for a suitable lifejacket or whatever, is there such a device. A new experience for me!!
You could try fixing a baby car seat to the hatchboards so baby is strapped in comfortably and can see its parent all the time,and can play /see every thing going on.
Some friends in my club did this for years with two kiddies. A buoyancy aid would be more practical from a comfort and warmth point of view, and provide adecent measure of safety.