No you are not doing the wrong thing at all, we all need some "us" time & I'd rather my bubs home in bed than dragging them out to a party with loud music, no sleep & so one IYKWIM.
I would just make sure your Mum follows the same routine you would. My Mum had never met Charlie when we went home at Christmas...he was 8months. Two days after we got to their place she took him home from the pub after tea, bathed, fed & put him to bed & he went down no probs at all - we were very lucky. Though now he's gotten very clingy in the past couple weeks & we will be home again in a weeks time & he will be left with MIL for first time ever........this could be interesting.
Remember bubs around that age are just starting to get clingy, they will grow out of it. Being at home should be good & dont forget to leave your dressing gown with her if that works.