I think they have overused and altered the word "donation" since it entered their vocabulary in the early 90s.
My take on it is if the parking and convention are "free" why insist on a daily parking "donation"? Let me ask a follow-up question: Can I still park the car if refuse to donate or don't have the money?
I think it is a revenue generating gimmick to either pay for the expense of the venue, generate a bit of needed profit, or most likely both. It's a little bit of word play: the stadium seats are free but the stadium parking isn't.
I think by insisting that people bring their own meals they are encouraging people to take their cars. Who wants to carry their bookbags and their lunches, and those of their children, on the bus?