DS1 was three last week and can now stay awake all day and not be too cross by bedtime as long as he has a nap a few times a week or when he's been to preschool in the morning.
He's more likely to wake up later in the evening after a bad dream if he hasn't had a nap.
I'll obviously keep him napping as long as he needs, but I wondered how old your children were when they dropped their last sleep as DS1's peers have largely stopped sleeping in the day.
He didn't sleep in the day on Friday, Saturday or Sunday and slept from 3-6 yesterday - went to sleep at 9 last night, which isn't massively early, I know, but slept till 7.30.