I think if you want it to work, it could. It does take extra planning though. I think I'd make the 2 parents sharing the spot figure it out on their own and just tell me which family is coming what day.

Or parents just have to pay for a full time spot. It sucks but they do technically need the spot to be able to use it whenever they want. Sharing parents would sometimes need to work around Inservice days if it wasn't their day at dc