Don't do it.
I'm having #2 myself, another girl, so I won't be having any "celebration" for her. When you announce you are having a baby, people who are so inclined to give you gifts will do so. For #1, we didn't invite out of town family (east coast/west coast) and most sent presents anyway,
If your mom is set on doing SOMETHING, here's a suggestion: have her take you (and anyone local, like your friends or whatnot,) to high tea or something, and you can toast your new little one. That way she can "do" something, you can celebrate, and you still can avoid rudely asking for gifts from people who can't come to a second shower, anyway. (And they are still totally free to send you gifts if they want.)