With DD1 (now 3.2) I didn't stay in for nap time at all, unless I happened to be in. She would sleep wherever her head hit. She was just that kind of child. No bother.
DD2 very quickly displayed herself as the kind of child that likes to be in her bed for sleeping. She will sleep on me if it is very quiet at home, or in the buggy or car, but not if there is any activity around. Far too interesting.
So, generally, I take DD1 to preschool, come back with DD2. Sometimes she will want to go to bed for a sleep at 10.30, other times she will hold out until DD2 returns from preschool.
My ideal is to hold her out, then they both go up to sleep for a couple of hours at about 1pm. However, if we need to go out, they both cope ok, and just go to bed a little earlier in the evening.