There's no etiquette problem with hosting your own Meet the Baby party, but I think it's more of a practical issue, as bah12 mentions. If you're the hostess, you have to make sure the house is clean, everyone has drinks, people are being introduced, etc. If someone else is hosting the party, you can relax more and just have fun with the guests and the baby.
It's totally up to you though. Open house and co-ed are both fine (and how I would probably host such a thing).