J.,
The best (and worst) thing about tofu, is that it doesn't taste like anything. It tastes like whatever you put it into.
I don't believe (AND ANYONE please mail me to correct me if I am wrong, since I intend to do this later on) you have to cook tofu.
You'll have to try silky to firm tofu, to see what your son likes. I would start with the silky. Drain it well, and squish (carefully, so you don't lose half your brick) it so you get as much of the 'tofu water' out as possible. You won't get it completely dry, but well, that's what I do. I haven't heard of any uses for this water, either.
You can add tofu to anything your son eats, and puree it together. It will add a little different flavor, so be sure to try it a bit before giving up.
Put it in applesauce, prunes or some other fruit or vegetable that he likes that is strong enough to mask it.
Start half and half, so that you get a fair amount of protein in before he either 'catches on' or gets full. (I do this with rice cereal. :) Sneaky!)
I would NOT try the tofu cheese, especially if he likes real cheese. You've got protein there already (and it does NOT taste the same, although it doesn't taste bad).
I use my leftovers in 48 hours or less (well, they rarely last that long anyway) simply because I don't know how long I have for them. They have always tasted good to me (cold or hot even) in that amount of time. I think the same holds true for chicken and pork, too, but I'm guessing there.
A recipe YOU might like is: prepare the tofu, put some olive oil in a fry pan, and sizzle the rest of the water out of it, until it gets crispy on one side. Then drizzle a little (measure before if you are watching your salt) teriyaki sauce, and flip it, adding a little more olive oil if you need it. You can add your favorite herbs and spices too. I've used oregano, basil, and a few others and it's turned out so well, even my husband eats it. :) I don't know where herbs and teriyaki stand on the baby's list of things to try, though, so you'll have to look that one up.
I also have it on good authority, that it makes a good sandwich, sliced, with tomato and pesto sauce (in lieu of mozzarella, and less fattening, too!)
Good luck!
M.