I should add that the only time its personally applied to me was for my engagement, it was at a VERY large park that ppl book certain areas of all the time and there was a hefty fee to do that... I have had park parties for my LOs before and as long as you don't pick somewhere that there's really only one option then should be fine... Everyones got a phone so its not hard to notify of a last min venue change I'm sure it'll all work out