Sorry, I know children's birthday party woes are rather mundane, but your twopenneth would be most appreciated 
A family friend has invited my DS to her DS's birthday party as usual. Normally, DH and I stay and watch the activity, and vice versa when it's our DS's party. Previous parties have included bowling, bouncy castle in a hall- that kind of thing. This year, she's doing the party at the zoo, which sounds cool, except I've just twigged that DH and I are going to have to fork out an entrance fee each. Other kids from school are coming, and might just get dropped off, but I know she expects us to stay, not that she's mentioned it's going to cost us this time.
I think we'll probably just go and suck it up. I can't be arsed to make waves. I'm just interested to see if people think this an acceptable expectation on her part, because I don't think I would expect it in reverse.