I often give my daughters a little extra cash when I know they need it, but im always open and honest with them when I do, and never give one more than the other, using a 'standard rate' which I set annually to make sure that no one gets more than the other when it comes to Christmas and Birthdays ect. The same applies to Grandchildren.
The problem I have is that the eldest two are from my first marriage, and the youngest two are from my second, and both Dads reward rates are very different, my second husband always gives his two daughters far more than the elder two get from theirs, and there is very little that I can do about it, as we are all independently responsible parents for our own incomes and bank accounts.
I would suggest to you Factfinder, that you treat all your Nieces and Nephews the same, and with out any secrets. If you give to one and not to all it can cause such bad feelings and family problems in the future, and no matter how hard you try, someone will let the secret out whether intentional or not at some point in the future. Recently, I gave my girls a sum of money towards house removal costs for the eldest two who both moved house within a couple of months of eachother. I made sure that the youngest two also got the same amount, one in Grocery vouchers to help fill her new freezer, and the youngest had the cash towards paying a large vets bill for her dog, and providing the expensive prescription food the poor dog needed, so they all got the same amount in the end and it was very honest and fair, with no fall.outs due to the pure clarity of the situation.