All good sound advice. If the younger one is teething - and in any case, tbh - stock up on Calpol <6, too. If the resort has a kiddies' club that accomodates their ages, get down there early on the first day, hang around for a while to make sure they're settling in OK, fix the 'minder' with a couple of icy smiles to make sure they understand how important it is to you that yours kids look forward to their daily couple of hours for the next fortnight, etc.