Well, it depends on the day - he is napping right now
In the morning he may take one or two short naps - like 30 -45 minutes. he takes a longer one 2-3 hours in the afternoon. In between, he is usually content rolling around on a playmat or in his exersaucer - unless he is nursing. I WAH 3 days a week, and so far have really had no need of outside help. Once he is mobile, that may be a different story
and I don't also have a 3 y.o. . .
I say try to keep him home with you for a week while you work and see what happens, and if you are able to get into a routine.
as for actual times . . . our day normally goes like this:
wake between 6-7
eat around 8
nap sometime between 9-10
playtime, interspersed with "natural" naps
eat between 11-12
nap between 1-3, sometimes until 4
eat upon waking
awake time generally until bedtime, between 8-10, usually with 2 nursing sessions between 4 and bed time.
all this is of course subject to change