Thanks so much for your input and advice. I think us staying calm will be the most important thing!! Remembering to keep them hydrated too.
I'm completely with you on manners, etc. It is not difficult to say please or thank you, excuse me, can I have rather than I want, etc (adults included!). My whole family is going (parents, siblings, nieces) and luckily they are all on the kids about being polite so at least we aren't with anyone that will just give in to them or with other kids that have no manners. My sister is as strict on her daughter (and will be on the 2nd who is due soon) as we are with ours so fingers crossed they will mostly be ok.
I think I'll just hope for no meltdowns just as we get to the front of a 30/45 minute queue for princesses or fairies or the fab 5!!
For distracting them in queues, have you ever taken bubbles? I know this would entertain my girls but worry they would annoy other people?