A group of Girl Guides Scouts all the way from New York has built a site for party invitations.
Best of all you can use it for free!
Personally I think they’ve done a great job of building these invitations hey but don’t take my word for it check it out for yourself. Just goes to show the great talent kids have today.
Here’s the link for the invitations:
http://www.hloom.com/free-printable-invitation-templates-for-kids/