D.D.
I just looked at a Youtube video about Fruit Ninja. Looks like a lot of fun.
I looked for you for about 45 minutes on the web and I can see why you are having trouble finding stuff. Most of the "fruit" paper goods I have found are of still life artwork. Frustrating. The only thing I found was at a website called partyatlewis where I found paper good with fruits on them that resemble the fruit ninja graphics. However, the background on this tableware is purple. I don't know how old your boy is, and purple background might not be cool with him.
You should be able to find some decent free clip-art to create your own invitations. You can buy precut invitation paper at most crafts stores, like Michael's or Hobby Lobby. They usually have directions for how to set up a Word document to print the invitation correctly.
I found honeycomb paper fruit at a website called devra-party. You could go with solid colored table ware and spice it up with a bunch of this honeycomb stuff.
Some party ideas:
A fruit "shooting" range. Set up plastic fruit on a ledge (garden wall, outdoor table, large cardboard box) and let the children use squirt guns to knock it off the ledge. You'll likely need heavy duty squirt guns.
Fruit toss. Pick a fairly sturdy fruit, like an orange, and pair the children off. Each team gets a fruit and they stand a certain distance apart. They toss the fruit from one player to the other, then step back one or two steps. Toss, step back, toss, step back. Do this until the last team drops and or squishes their piece of fruit. Of course, you can make the game more interesting if you use a less sturdy fruit like a strawberry. LOL.
A foot race where each child has a plastic spoon with a grape on it. They have to hold their arm straight and run to the finish line. If they drop their grape, they can't keep running. Whoever gets to the end with their grape on their spoon is the winner.
Duck, Duck, Goose! With fruit substituted. Lemon, Lemon, Kiwi!
Good luck.
