^^^ we do this too, Underdog, but we share a calendar through iCal with all our daughter's karate practices, appointments, back to school nights, etc. We are both responsible for entering things into the calendar as they come up. When he updates it, I get a notice and when I update, he gets a notice. Easy peasy.
When we exchange the kid (I hate that), we talk about upcoming things on the calendar and discuss places where we might need help. For example:
"D7 has piano on Tuesday but I think her book is at your place. Can you bring that over before the weekend so she can do her homework and practice?"
So far, I've only had to ask once, maybe twice (this is totally new, it used to be 10-12 times I'd have to ask if I needed his help with something).
Anyway, it works for us and there are NO excuses. It's in the calendar. Done.
