Hun first suggestion don't both with them if they dont bother with you ecspecially if they are going to act like that.. It's not fair on you or you ds
Also how dare they go elsewhere on such a special day for your ds!
I would be furious also that's just ridiculous
I think you should pull your brother aside and ask him why he is being so disrespectful to you..
Maybe it's his wife that's the mastermind behind all of this and your mum shouldnt make excuses for things that are obviously inexcusable
Massive hugs babe chin up hun your so obviously the mature one out of the two...