We had the same problem, mums returning to work and of course the sleeping issues, 'Mine sleeps at 10.30 to 12 so can we change to 1.30pm' etc. Of course we didn't change anything because as we all know routine changes especially when they cut back to one sleep a day. As time went on the mums who went back to work have now had their second bubs and so still come along on the orignal day. All but 2 of the mums who went back to work arranged not to work the day we had play group. I guess what made it easier for us too was that the regulars (me and 3 others) who turned up every week unless we were sick were happy with the time and day. The others turned up only when it suited them so we felt why should we change to accommodate them IYKWIM? Its a hard one and depends on the group but keep in mind you aren't going to please everyone. Perhaps if you have a large group,the ones who can't make the orginal day can start their another group on a day and time that suits them? We had a large gourp of 10 to start with, we are now down to 8 and we have 4-5 regulars so the day is always great regardless of who turns up.