N.B.
Definately see what hes up for. You can get a new seat similar to a Potty Pal, where it has an additional flip down piece (its all attached) for a kiddie size seat (So it has the lid, a kiddie seat and the adult one all hinged together)
http://www.pottytrainingconcepts.com/CON-207-600R-02.html
Then definately have a step stool for at the toilet, and if needed, another at the sink. It can get to be alot of stuff..but the more you keep him independent, the better for all of you!
I do home childcare, but do all I can to train at the regular toilet and without rings, etc if I can. I train kids young (22-28 mos)...sometimes it works according to my plan....sometimes they want the assistance pieces.
Good luck!