Before we had MoleDog spayed she bled for about 10 days but I think the season lasts alot longer than the actual bleeding, about 3 weeks IIRC
I wouldnt necessarily not take her away if you planned on long walks with her etc as a nice part of your holiday, you just need to be vigilant and keep her on her lead. Thats all we used to do.
Do get her spayed as soon as you can though, its much better not having to run around after MoleDog with tissues and we dont worry anymore about adding to the already overcrowed rescues with an accidental litter of MolePups
Yes, she will probably be at her most fertile while you are at CentreParcs, so definitely, definitely don't take her, and if you are not 100% confident about your parents' security arrangements, find a boarding kennels quickly!