I would go with the swim vest. You would be able to put it on and take off as needed, while a floaty suit he would have to keep on, and may feel bulky and uncomfortable while just playing on the beach. A jogging stroller works great on the beach. The smaller umbrella strollers are not good for that. My child has a wheat allergy as well, so bring plenty of gluten free food. An epi-pen is a great thing to keep on hand just in case. Have a great time and take lots of pix