Yeah, I have to say, I find it weird that she is doing it. I know I wouldn't be - not with my first baby still only 3 weeks old! Stuff the tired issue, I want to be with my baby, not taking someone else's to swimming lessons. I find it odd that she is willing to do it, but more odd that he is going to a swimming lesson at least ONE of his parents can't attend.
What is she going to do with her baby while she is doing the lesson with your son?