There are probably some motorhomes out there that have a tub. Although the only type of tubs I personally have seen are rather shallow. As someone mentioned, most RV showers do not put out a lot of pressure. Too bad you can not have your son test out an RV shower before hand. The tub thing will definitely limit your search. Also, if you plan on doing any camping without sewer hookups, filling up a tub will fill up your gray tank fast.
Are there any other kids in the family? Will it just be you and your 5 yr old? As far as type goes, that will have to be up to you. You will need to figure out what you want in one, the size, budget and etc. A Class C typically will cost you less than a Class A. Both have their advantages and disadvantages....More of what you are looking for as I mentioned would help.
But being that we have a Class C right now, I would say they are normally best for a family and/or getting outdoors more. Think of them as more utilitarian than Class A's. Not always, but for the most part. Class C's sit lower to the ground, so less steps to climb. Driving one is more like driving a van and little less intimidating.
Please tell us more of what you want or what your expectations are. Also, wht kind of car will you be towing and how? Tow dolly or 4 wheels down. You will need to consider how your car can be towed, the restrictions on it and the cost.
Brian
2013 Thor Chateau 31L