Crepe Paper Shamrocks!
The supplies couldn't be easier. Crepe paper, a pencil and school glue. I used an art canvas I had
laying around, but as a kid's craft project, doing this on paper or cardstock would be fine too. I found the crepe streamers at the Dollar store.
First thing you need is a shamrock outline. You want the shape to be pretty large and over-emphasized, since once you add the crepe paper ruffles, the perimeter won't be as obvious.
And stick it down to the canvas/paper:
Once you have the outline finished, you can fill in the rest of the shape:
A few other green items, and you get a little St. Patrick's day display that isn't at all childish.
The whole project took a little less than an hour, and cost $1 plus the cost of the canvas (I think it was around $3). It does get a little redundant, and the kids did lose steam about half way though, but it wasn't hard at all.
Do you have any children's craft projects integrated into your decor? If you don't, it is definitely something to consider!