I live in a very Catholic area, and First Communion gifts are actually larger gifts - $50 - $100, depending upon the relationship. A grandparent/godparent will usually give more. If it's someone you are not close to, a $50 ($25 face value) is common.
We don't have a lot of family here, so no party (we all go out to dinner), but most parties are sit down dinners at restaurants (people here start booking in the winter for the spring, since we have 5 Catholic churches in 3 - 4 miles).