Invite friends who can creatively impart some personal advice on raising children (particularly if they have children the same age or gender as her stepchildren). Make sure there is a lot of wine so she gets honest advice. Invite other stepmothers if they are in your circle of friends. Buy several Step Mothers Rock t-shirts made, pass them out to all the shower attendees to wear at the shower. Make sure to get one for her and her stepchildren while you're at it. Play silly stepmother shower games. Get a cake from the local bakery that says "Congratulations Mommy!"