Great to see your name on a post! Don't be a stranger. Now that you've got high speed access you can zip right through these forums.

I'm not following how your words relate to your sketch, unless your sketch is a "before"? If you are planning to lay out your bathroom with your toilet perpendicular to the 3 1/2' wall, that won't meet code. Code requires either 21 or 24 inches from front of toilet to wall - just about the minimum you can get away with is about 4', 4'3" would be better. Is there any way you can squeeze another 9" into the plan? if you can, it's definitely doable. My downstairs bath is pretty minimal, it's about 7'6" (I think, maybe 8'?) x 4'3" and it accommodates a stall shower (30x48 insert), a regular elongated toilet with plenty of knee room and a 27" pedestal sink with a pocket door. It's not huge but we've been using it as our primary bathroom since november :/. There's enough room to stand in front of the sink and pass the toilet to get to the shower.

We had heard that Toto was not going to be selling residential tubs anymore. Hope that's not true--our 1525's are really nice tubs (read about them here on GW). If you can still get a Toto tub I think you'll be happy with it! FWIW, we have a Kohler cast iron shower pan in our guest bathroom and it's nice, too.

I still have my stool too :), and I agree on the universal access sink height, which is in between low vanity (31 ish) and tall vanity (36) height. Its hard to say without knowing the layout of the bathroom whether the wheelchair accessible sink is feasible (say if the bathroom itself, isnt.) If you are in the framing stage you may want to consider both the layout and such things as blocking for handrails and such. It may seem premature, but my parents moved into a new house when I was in first grade and still live there. Now at 81 and 85 there are some real accessibility issues with the baths (and stairs) in a house that my parents refuse to leave. Watching my mother navigate some parts of the house is like watching someone climbing a rock wall...its not fun. I think you are really taking a lot of consideration if you are considering making modifications for your young children, so, look into making some accomodations for your parents (and yourself!) as you age, while you are in the process.