when to book spa appointments

DH and I will be going away for one night to an inn/spa. I don't know if we should book massages for the day we arrive or for the following day before we go home. I'm thinking the day we get there so we're all relaxed, have a nice dinner and then a nice night in front of the fireplace. But then I'm worried that if we leave late in the day (we have two kids and you never know) or hit trafic then we may feel rushed/be late. On the flip side, do we really want to get massages and then go straight home? I just don't know. When would you book them for?