You could easily race them on Sunday, depending on gluing method. I would suggest against it though, especially if you have never raced on tubular cross tires. It takes some getting used to how they feel at low pressure. Also, you don't want to find out your glue job didn't hold during the race! If this is your first glue job on cross tubulars I would really advise against racing on them the next day. Gluing cross tires properly is much more important than road tires.
Get on a cross bike.... you'll like it ;)