Hi Carriemum,
Not really much help but wanted to say it sounds very familiar. My DD falls asleep sometimes in the afternoons, I can't wake her and then she is VERY grumpy! It really is better for us if she doesn't fall asleep even if she is really tired, but that is easier said than done!
I have noticed DD needs quiet play time when she gets home from kindy, playdates and shopping are really not a good idea. If she's had that hours playtime at 2pm she is much better later. II hope it is just a stage and by the time they are 4 they need that nap less often.