how much to charge a daycare?

[FotoSynthesis]

I know another how much to charge question may be annoying! I'm at a loss though. I've been asked to do "school portraits" for this woman who runs a daycare in her garage (she converted it into a classroom). I haven't gotten all the details because I don't wanna get into more information without having a price to tell her. I just started doing portraits so I have some but not a ton of experience. I'm just at a loss with what would be fair to charge. I don't want to go too high but I also don't want to go so low that I end up making hardly anything.

Any help would be greatly appreciated!