I am far from being the jon boat pro. My second hobby (aside from bass fishing) involves restoring, repairing, updating, and using aluminum boats. So, I spend my meager free time, learning what I can, and getting as much experience as I can.
I haven't had any experience with the rhino lining, but I have not heard many good stories about it. If you want more info on that, join bassresource.com, and PM member LowBudgetHookers. Or, PM me what you want to ask, and I will forward that to him (Jim, have you asked him to swing in here from time to time?)
As far as the deck, if you can afford the aluminum, or find the right used stuff, it would be great. It is light, and it won't rust, bust, or collect dust. Won't rot either. The slippery factor can be solved by a layer of cheap indoor/outdoor carpet. I would recommend doing something like that on any jon boat that is too small for a conversion. I am just waiting until we can do it to our 12 footer, but none of our boats have gotten any attention in 2 months (either fished from them, or worked on them - my family is way too busy, and unfortunately, dad and I (I am 14, not a big ole baby still living at home) have to take the hits).
As far as those seats, the idea is great, but the quality is shoddy, from the ones I have experience. The mount is made from a non flexible, brittle plastic, and isn't in the strongest shape. Ideally, that part would be made of aluminum, and we have parts of the brackets in the shop, that are awaiting the replacement of that plastic piece, with an aluminum one, when we have the time to mill it out. Your best bet is to probably to make your own design to hold the seats on. Currently, our seats are mounted to the swivels, and those swivels are mounted on a piece of 3/4 inch ply. Then, we used a ratchet strap, around the bench, to hold that ply down. Started out as temporary, but it worked so well, we haven't yet bothered to change it.
That boat probably shouldn't have trouble holding the weight you want to. When your kids get older, you will have an excuse to get a bigger boat, and build up the navy.