I left DD for wedding plus reception at about 7 months, but we were maybe 30 mins away, I left her with my parents. She was fine but I missed her as were loads of other babies there. Also had forgotten would need to express (apart from 14:00 to 24:00), so not comfy. If I had time again I would have popped back between wedding and reception so I would say if you can get MIL to mind your little one close by that is a good option.