I have 3 kids, so I'm not dividing the budget into as many shares as you are. Our kids are 15, 13, and 10. We now do $100 per child for Christmas and $50 for birthdays. We didn't spend as much when they were younger.
Now they are older and want electronics and cameras, so they want the dollar amount so they can put the money toward the item they want. They ask for money from their Grandparent's, too. It's easier for me, but pretty bah-humbug. They even do their own shopping--reading reviews and finding the best deals, so their money goes further. Again, very non-magical--but I guess they are learning good life skills.