Yes. I agree with you on her comment. That is a bull-manure statement. Selfish to spend time with your son? What an idiotic statement.
It was designed to attempt to make you feel guilty so you would let this go her way. Ignore, and do what's best for you.
Avoid the temptation to point out her selfishness. Just be calm, strong, and firm. "No, W. I've thought about it, and I will continue to pick up S. He is in great hands, and will come to no harm in the brief period of time you're not there. I cherish my time with him, and am not willing to accommodate your request."
