Back in the day we called them belly boats. A truck inner tube with a canvas cover and seat. they were inexpensive and fun to fish from. I used one for over a decade and can tell you they are fun to fish from and have some advantages over a kayak or a jon boat, the least of which is portablilty. Many of the the current offerings are self inflatable, or at the least have a self contained pump, either of which allows you to deflate them after use. You will be limited to the amount of gear you take along only if you don't think outside the box. I towed extra gear on a platform I attached to a bike inner tube and was able to keep the float tube free of excess gear.
Two things that made it's use a learning experience were the fact that being in the water I was able to feel slight changes in the water temperature. You will learn quickly how big a benefit that is. The other was learning just how strong a bass is. I lost count of the times a decent sized fish towed me 50 yards or so before I could land it.
The biggest drawback is the speed at which you are able to move around. That, too, I found to be beneficial as I was able to concentrate on the general area I was in before moving on.
A word of caution if you decide on an inflatable, get one with a strong exterior. More than once a hooked fish imbedded a treble into the canvas as I attempted to land it, one time puncturing the bladder. Oh yea, if there are snakes in the area, they are attracted to your little, floating island so stay alert.
As for models, I'd look for one that you will sit high in and that has some sort of apron and places to store some gear.
Happy Birthday, and enjoy your gift.