Gift giving or not or do on to other as they do?

My younger brother had a graduation party and my Aunt and Uncle gave him a card so did her adult daughter and fiancee that's it just a card and they were all 2 hours late. I was there when he opened his cards so when everyone else gave him money they did not. My question is My cousin is getting married in two months and I think my mother should just give the cousin a card also and that's it. Everyone has the same financial ability. My mother spent alot of money on my brothers party and it was very nice. My mom is always trying to make everyone happy but I'm pretty sure she should just give a card since both my Aunt and Uncle and the cousin both felt o.k. with giving my brother just a card?