fabric for superhero costumes?

We've finally gotten to the point where my kiddos are requesting SUPERHERO costumes for Halloween.  What fabric do I use?  I need something stretchy but also kinda indestructible (at 2 and 4, they aren't easy on their clothes).  Easy to sew and not too expensive?  I'm guessing a knit with spandex or something in it, but I've never sewn with that sort of material before, so I'm a bit cautious.  I've got lots of experience sewing with quilter's cotton, and a little with cotton jersey.

Obviously, I have a few months, but I like to get a head start if I can.

I made my son a cape out of cotton lame.  I think it was at JoAnn in the Christmas fabric.  It worked out really well for the cape.

I think a spandex knit would be a really good choice for the costumes themselves.  spandexhouse.com or spandexworld.com both have excellent selections of spandex fabrics.  A nylon spandex would probably work the best. 

As for sewing these fabrics, if you have a serger, it's super easy to sew them.  If not, use a narrow zigzag (.5 width and 2.5-3 length) and a 75/11 stretch needle.  You could try a ballpoint needle, but if your machine is like mine, it'll like the stretch needle better.  HTH.

Thanks for the tips!  I really appreciate it.