If you need something that's relatively easy to do build things with
gumdrops and toothpicks. I got the idea from here. I started out with a 5 pound bag of gumdrops (spice drops if you like) and a box of toothpicks for each person (flat...though I would recommend the round as they're stronger. Flat was just what the store happened to have)
Each person got started building, but we ended up with partner's
Tiny's singing a song while Dad works on Gumdrop Tower
Mowg's building a man
And a place to feed a dinosaur
Let's do it together!
The Final Gumdrop Tower
(and two builders)
Note the carefully made color pattern
Mom and Mowg with the dinosaur building and the man
Note the very random colors on the dinosaur
Some of the building mess
We had a few colored round toothpicks and they were much more secure.
Far easier to work with.
If you're wondering about something very fun to do without much prep
(or clean up--except deciding what to do with your creations) This is perfect.