INVITE
Use a written invitation - it's a good way to manage expectations and let other parents know what's going on (even if it eventually gets circulated by e-mail.) Spell out:
BE NEIGHBORLY
Advise your immediate neighbors of what's going on. Give them a copy of the invitation and drop off a copy with your local police as well. They'll appreciate being kept in the loop.
SEEK VOLUNTEERS
Don't hesitate to ask for chaperone help. After all, they're not all your kids.
OBSERVE
Tour your home and property during the party. Believe it or not, your presence is welcome relief to most kids.
LEAVE LIGHTS LIT
Light up the place..."Tis better to see you, my child!"
BE VISIBLE
Don't hover, but being seen, more often than not, prevents problems.
ENJOY
That's what the party is supposed to be about!
BE DECISIVE
Of course there are other things you can do to ensure that the kids have a good time. Being involved, while not "in their face", will add to the relaxing enjoyment of all.