I personally do not exclude for hand, foot and mouth disease itself - so unless the child has a fever still or is so miserable they cannot eat or cope with the demands of a group program they can attend.
It is not listed as one of the exclusions on our Public Health list for group care ... HFM is kinda like the common cold for most people it is an annoying thing that passes without treatment cause it is a virus - for others they have a lower immunity and end up with a nasty case of it and end up being home because of those 'extended' symptoms not the 'virus' itself but rather how their body reacted too it.
My understanding is that is contagious before symptoms are present through 'saliva', during the outbreak through the liquid in the blisters and is still contagious for WEEKS after the blisters are gone it is carried in the stool of anyone who had it - so when the kids do return if you exclude them make sure you are on top of hand washing with the kids and if you got a bum itcher whose had HFM really keep on top of them to keep their hands out of their pants cause if they itch themselves and touch surfaces - it is being spread as well. (not that we do not keep on top of them to keep hands out of their pants anyway but the risk is even higher to spread germs)
ETA .... link from the Health Unit in my area
http://www.healthunit.com/article.aspx?ID=10195