not sure if I want to keep it short or go longer

If you prefer short hair, and don't care about having long hair, growing it long to donate it is a very nice thing for you to do - you go!  If, however, you prefer long hair, you should be aware that this organization has stated in the past that they receive 1000-2000 ponytails a week, and though they've been running for 10 years, they've only made 2000 wigs for needy people (some of whom they charge for them -on a sliding scale).  They also used to say it took up to 15 ponytails to make one wig.  If you do the math you see they only use up to 2% of the hair they receive for needy kids.  Since the head of the place stopped listing her salary on the bbb reports, we can only assume she's getting pretty rich selling the rest of the hair (or she'd be proud to say not, right?).  They stopped posting all of those numbers on their websites when people starting figuring this out. 

Personally, I don't think all of that is necessarily all bad.  If you check charity navigator, you will see that many heads of many charities are pulling in over 100,000 bucks a year, so its really not that uncommon (but I don't personally choose those charities when I donate money).  My point is just that anybody who doesn't care if they have long hair or not, yes, go for it!  They do need people to keep donating to continue to make wigs, which are really great for the kids who need them.  But if you love having long hair, those odds of it going to good use aren't good enough.  Donate blood or money instead.