With cresta/Leger your holiday must come to a minimum of £500 if you want to use tesco vouchers and must include travel (eg ferry if you're driving or Eurostar/flights). you can't get family and friends to save up cubcard vouchers for you anymore - we used to do that and then they changed the rules - cost us a holiday!!! Bummer!! The clubcard vouchers have the holders anem on and they MUST be on the booking or tesco won't pay up.
We're currently waiting for the stay 2 nights get an extra night free deal with cresta.
I think minimum amount you can change is around £2.50 worth = £10 off
Good luck in tracking down a cheap deal!
Would recommend the Disney hotels - nice to be able to have a short walk to your hotel in the evening!