Oh dear, I am going to ruffle feathers, because, much as I appreciate how you have had to take second place to MIL over the yewatrs, she is now presumably of an age and if my DS and DIL lived 30 mins away I would hope to see them once a week - especially if my memory was starting to go. How about a compromise? You go over on a weekday one week and he goes the other week. If he only works 4 days a week he could go on his free day, or you/he could bring her over to you. Perhaps he is under her thumb, but why must Saturday be your "special" day especially now you have retired? I am afraid I fear a power struggle here and frankly if ti came to that it looks as if his mum would win - so compromise . We'll all be old one day and possibly alone.