Yeah I would either get someone to go earlier and reserve a few tables, hubby has done this for a few of his mates before. Or I would be prepared that you might not get a table. Personally I think it would be rude to rock up and ask someone to move from a table because you had 'reserved part of the park'. I have to admit if I was having lunch with my family and someone came up and said they wanted us to move I would probably tell them they should have got there earlier.