Wow! Thanks everyone for all the advice! We ended up creating the registry.com registry and that is apparently completely acceptable. (Thank goodness!) We live pretty far from my family, so they couldn't really help out in person much, but they do love throwing big parties. My mom is giving some non-gift suggestions as well now, like museum memberships, so I think they'll suvive, but being able to have the registry.com was a life-saver for us!
I'm perfectly happy to smile and graciously accept gifts I'm later going to reject, so long as I haven't registered for them.I felt like registering for a gift I didn't want would be dishonest and unfair to my family, so having the opportunity to find gifts I actually wanted was such a blessing. Thanks again for all the advice and support!