It's up to you, some charge a holiday fee, some charge full rate for both children, and some say "see ya" and only take both children if it just so happens that two spots open up when mom needs them. Don't sell yourself short and lose a ton of money to keep a spot open. You never know, the family may move, mom may decide to stay home longer etc and you will get screwed. If it were me and I had two spots available now, mom would have to either start paying full rate for both or keep the oldest in daycare during her mat leave and hope a spot opens up for the infant, or mom takes her son out of daycare during her mat leave and hopes that you have TWO spots open up when she needs them which is unlikely. Do what's best for YOU not this family because when the time comes they ALSO will do what's best for THEM.