Hmm, well there are a few ideas here for ornaments http://funadvice.com/r/14mb3gtb3l2 they seem simple enough to make, but I don't know how to really get a couple three year old girls into it. Maybe have a pre-made one so they can see what they're trying to make? You could show them one and ask if they'd like to make one for themselves. They might need help gluing things and such though. You could always fall back on colouring Christmas pictures if they are too young or don't want to. Just some ideas.
Not exactly sure if this what you are after but I think paper mache would be a fun thing to do or give to a little kid....Blow up some balloons and try to put these balloons together to form a shape of an animal, eg: a pig or horse and then glue small pieces of newspapers all over the balloons, layering as many layers of pieces of newspaper as you can until the balloons are wrapped in hard coated newspapers. You can get the kid to paint or decorate the paper mache.
buy s styrofoam ball, about the size of how big u want the ornimant then buy a whole bunch od sequences (spicificly the ones with wholes in the middle) and just have the kids put on the place of the ornimant where they want it and stick a pin in it or glue it which ever u prefer. until the whole ball is filled with sequences but remember to pin or glue a ribbon on the top so u can accually hang them. lol :)
If you go by the dolllar tree i noticed last time they were in there, there is an entire section of make your own ornament kits for young children. The kits are just a dollar each and have everything you need. There were some that made them out of felt material, ornaments your blow up, some your paint with washable paint, etc.
with them...im a nanny for twin 3yr old girls. i feel like it would be fun, but at that age they're too young for most stuff. i dont want to get in over my head lol-
oh they'll want to lol- they want to do everything theirselves. thank you=]
Are you making them with three year olds, or just for them?