This thread makes me feel sad, and honestly I think if it were the other way around (a woman wanting to see her mum and her DP getting annoyed by it) the responses would be different.
11 months may seem like a long time to others, but unfortunately there's no set length of time where people who have lost someone can suddenly just say, 'oh alright I'm fine now' - it just doesn't work like that.
I would be incredibly proud that I have such a loving DP who cares for his family so much - family is NOT just the nuclear family of parents and kids, but the extended family as well, and I think that is forgotten quite a lot.
I do agree with the previous poster who suggested that MIL could pick up the children once or twice a week - that's a great idea, will help to get her out and about a bit more and they will be closer with her.
The idea (as some previous posters have said) is to encourage MIL to meet new people, to get out of the house a bit more and to start enjoying life again. However, it's not easy, and having the support of her lovely son must mean everything to her.
Please don't forget that your DP has lost his father, too.