Experience with LLC vs not-for-profit?

There is a new theatre group in my area that is looking for guidance and I'm at a bit of a loss regarding some particulars. The group has chosen to become a LLC instead of applying for 501(c)(3) status and has been absorbed by an umbrella corporation. I'm mostly interested in how this will effect the ability to receive donations and corporate sponsorships. Also, are there any others problems/concerns that might arise given their status?

I should note that no one is receiving pay and they are essentially running it as if it were a not-for-profit community theatre. The bulk of the money is coming from the owners' pockets.

Katie