What are some low cost snacks, appetizers and/or Hors D'Oeuvres that can be served for a kids birthday party?

I am having a birthday party for my 3 children. It will be all family but the party is kind of late in the day for lunch and way to early for dinner. I was wondering if any one had some great ideas for something to eat with out making a meal and hopefully doesn't cost much. I have a very low budget left for this party. I am expecting about 18 adults and about 13 children (infant to school age). ANY Great IDEAS out there??? Thanks in advance for all who share their ideas. :)