Could I have some advice on salary/benefit negotiations?

I just got a formal job offer from the company where I interned last summer, and it's about what I expected/think I'm worth. I really want to just take the job, but I don't want to leave money on the table; my understanding is that expected value of trying to negotiate should be positive regardless. On the other hand, the company basically knows I'm going to take the job, so I don' t believe I have much power in these negotiations.

Since the whole reason I want more money is to be able to donate more, I'm thinking it might make sense to try to negotiate for employee gift matching instead of a greater salary. However, as a small employer, I don't believe they have such a program for any employees. Is it still worth trying that angle? If so, how might I go about it? Thanks a lot for the advise.