Hi Shane,
I've got lots of information for you - hopefully I can fit it all in!
Resorts - All of the WDW resorts have life jackets available on a first-come first-served basis, and they are permitted on the waterslides. The waterslides do not have any age or height restrictions, however only one slider at a time is permitted.
Water Parks - Complimentary life jackets are available at the water parks, or you are permitted to bring your own. Like the resorts, the vests may be worn in the pools and on the slides. To see all of the height restrictions, click
HERE and use the filters on the left hand side to select the water parks and applicable height. Personally, I prefer Blizzard Beach for little ones - I found
Tike's Peak to be very user friendly for families with little ones (nice layout, good visibility etc).
Disney Dream - Life jackets for use in the pools are not available onboard, however you are permitted to bring your own Coast Guard personal flotation devices (PFDs), water wings or flotation sewn into bathing suits. The
AquaDuck water coaster requires that guests are 48" tall, and will allow two riders. The
Mickey Pool is for smaller children, and features a slide for guests between 38" - 64" tall. Only one slider is permitted at a time. Unlike most waterslides, this slide does not exit into the pool, it simply finishes in a few inches of water and the child simply stands up and walks out the end of the chute.
I hope this helps!