D.B.
Actually, I am surprised that, after several years in this program, you don't have any contact info for the others. Is that a daycare center policy? Most places print a roster (with everyone giving permission to have their info listed, or else opting out). Have you saved intro from previous party invitations?
I think the answer might depend on why you are leaving. If you are dissatisfied or have had a problem with management, then you can't ask for their cooperation in getting the social info out to the other families. If you are leaving because he has outgrown it or you are moving or need something closer to work, that might make it okay to involve them.
Assuming everyone feels the same way you do about good friends, then I would think they would WANT your contact info and to know that you are leaving. Otherwise you can verbally inform people you see at pick-up & drop-off, and maybe see what they think. I think you have to go by the customs of the center.