I like the idea of a reusable piņata. If it's reasonably salvageable, keeping the thing makes perfect sense.
I've heard of young children who had a bit of distress when a piņata in the shape of an animal or person was destroyed. Having Elmo attend several parties is a nice idea.
We also keep and reuse gift bags. So long as they're in decent condition, they can be used to package gifts for others. If the seams are starting to go, we'll tape them up and use them to package gifts for each other. There's nothing wrong with that.
One woman from our church texted me earlier this week to see if I'd be interested in helping her organize a costume exchange. I think it's a great idea, as expensive as costumes can get. One year my middle son wanted to be Harry Potter. I swear that costume ended up costing us about $40, at least because all that was in the bag was the robe and that cost at least $25, then you had to buy the glasses, wand, and Gryffindor tie separately at $10 each.
So the thought of exchanging costumes is a great one, I think. I've taken to putting together costumes from what I have at home, while just buying maybe one or two extra pieces. This year I'm wanting to dress up as Tonks from Harry Potter and am trying to figure out how I can pull that off without buying much more than a pair of fingerless gloves for $10 from Hot Topic.