I'm going to go out on a limb here and say I think this is more to do with the fact that it will be her taking him and not you period. I understand the driving thing, I really do - I've been there and done that myself so I know at times it can be hard. But I think you should give her a little credit. She's an adult woman, with a babe of her own and she probably knows her limitations. Is it any different if she drives herself and her baby somewhere on a Tuesday or a Thursday? Of course it's not, but you don't seem to be worrying about that so much as the one day a week she will have your son in the car with her. You're only assuming that she is sleep deprived too - maybe she goes to bed early so she can catch up on sleep? Maybe she has other support to help her take a nap during the day?

I really wouldn't be worrying about this. I think you have to think about the benefits the actual swimming will be to your son and not worry about her.