Child's Nap

The average child's need to nap and on a napping schedule:

1) Newborns sleep as much and as long as they need to.
2) 4 and 12 months, babies move to two naps a day, one in the morning and one in the afternoon, each ranging from 20 minutes to three hours.
3) 2yo, most toddlers take a single two-hour nap in the middle of the day.
4) 3yo, some will have given up naps entirely.

As with most other sleep issues, consistency is essential.

Some says, by 15mos some children start to give up their morning nap. If you can, have your child nap in the same place that he sleeps at night. A set nap time in a set place will ensure that he gets the sleep he needs. The best times for naps are mid- to late morning for morning naps and early afternoon for afternoon naps. Don't let your child nap past 4 in the afternoon, or he'll have problems going to sleep at night. At least three hours should elapse between the end of an afternoon nap and bedtime. Make nap times consistent

And Other says, two naps are no longer predictable, although putting your child down for a short time in the morning and again in the afternoon is recommended. By the time he's 18 months old, don't expect more than one nap per day, usually between noon and 2 p.m. Don't let your child sleep past 3, or you may have a harder time getting him to bed at night.

Anyway, I think no forcing them to sleep as it should be an enjoyable task to do.