I think this is really regional. Everyone in my area sends graduation announcements and senior pictures, and I don't believe it's viewed as a gift grab - in fact, when we run into family friends we haven't seen in awhile and they know something like this is coming up, they say "Please be sure to send an announcement when graduation gets closer!" I've had a couple people do this since I've been pregnant also, about birth announcements. We send/receive those around here also, as a way to share some early cute pictures of the new arrival and the statistics - particularly for those family members who aren't in the area, might not see the baby for awhile, and would like a little keepsake.
Family members and friends who want to give gifts will and those who don't, won't - whether you do announcements or not. If you're sending them with the spirit of sharing your child's accomplishment and not just coming up with as many people as you can think of in hopes of gifts, I see nothing wrong with it. You should be proud.
Many people *will* give gifts, and I don't think there's anything wrong with that either. Standard pre-printed announcements will make no reference to gifts, but if you are making them yourself and would be uncomfortable receiving them, I think a small-print "No gifts, please" is simple and standard. Just be aware that those who want to send gifts will probably do it anyway, so unless you are adamant I would not mention gifts at all. I think most commencements are limited in how many guests people have - if you are concerned the the announcement will be confused with an invitation and you are making them yourself, you could state just the date of graduation and leave off the time and location.
I'm typically pretty sticky about etiquette (registry info in invites, etc) but I don't see an announcement as a request for a gift. We've received lots of announcements in the past and given gifts to those we felt appropriate and not for others. I'd be surprised to not receive one, especially from close family and friends.