Definitely won't reward cash for grades, DS2 has additional needs and will find it a lot of work to get 4/5, DS1 could get that with no work whatsoever so would be hugely unfair.
I hadn't even considered getting a gift for DS1 as I guess part of me feels its for his benefit he should work hard but now I feel a bit mean lol. To be honest he could have worked harder but will come out with a good set of results anyway I think. He didn't not work but didn't sacrifice too much social life really. We are going to watch the cricket that night so I think he'll assume that's our celebration. He also earns very good money so I think taking him out for coffee/cake he'll appreciate.
I got cash for grades as I was quite clever at school but did nothing so was predicted dreadful grades as didnt even turn uo for mocks. I ended up with As and Bs as wanted the cash haha so it's definitely a good incentive for those who need a kick up the backside.