I didn't have my nephews at mine.
It was a weekday so 2 of them were at school anyway and the other was 18 months old and we just didn't want him there
His mum (my SIL) at first said what am I meant to do with him and I said leave him with your mum (who looks after him 3 days a week anyway) she said OK and that was that!
If she had said she wouldn't come because of it I would have said fine. I doubt Mr HoGi's brother would have missed the wedding because his kid couldn't come, he regularly goes on holiday and leaves his wife at home with the kids!
A friend of a friend got married last year and the venue had a policy if there are more than 10 kids there has to be a children's Entertainer during dinner!! I couldn't think of anything worse during a wedding.