Cats are tough, but i have learned from experience that the sound of power tools and banging that goes with renovation is not their favourite noise. It would be all the scarier if they were in a strange environment without you around to show them it was all OK (i.e. by not making a fuss of them when they showed fear, but by carrying on as normal - the take their lead from you on the nerves front I have found). So either the in-laws or the cattery are the only sensible option. From what you seem to be implying, relations are not all that good with the inlaws, at least from your perspective, so you will be tense and stressed from the move, from project-managing the new work and from living with the Inlaws - not a recipe for keeping a nervous cat calm and happy. Personally I would be going the cattery route ...