Would you allow your preschooler to go for a sleepover?

I agree with Hui. Personally, I would not. At this age, preschoolers are highly to regress during bedtime. They need to feel secured and the most secured place for them would be their own abode where they can see familiar faces--even when they wake up in the middle of the night. Another thing to consider would be bed-wetting which is very common at this age for it might be bothersome for the host family.