My son just turned 7. What we do is similar to sleepypeanutsmom. We started giving him allowance in January so are just coming to the end of the first year of allowance. It has been a great success!
We use the Moonjar (moonjar.com), but you can use any 3 containers. We give our son $5/week. $1 goes into "Sharing" and we let him divvie up the remaining $4 into "Saving" and "Spending" as he pleases. That means at the end of the year, he has $52 to share - give to others. It has been really wonderful to see that throughout the year, he has chosen to give to a public radio station that we listen to and a local kid's circus. He's figuring out how he wants to give his remaining "Sharing" money.
If he is given money as a gift (for birthday, etc.), I consider it just that, a gift, and let him do with it as he chooses.
If you set it up initially that either a specific percentage or a specific amount is designated to "Sharing" (or whatever you want to call it) each week, then there is no need to try to figure out at the end of the year how to separate it.
So, for example, for your 10yo, if you give him $10/month and designate that 10% ($1) will go to "sharing" he will have $12 to give by the end of next year to give to others!
Our son has $4 to spend/week and he quite patiently will wait those 5 weeks to buy that Lego set he really wants.
At age 6-7, the savings thing is hard for him to understand. For instance, right now in his "spending" box there is over $20 that he is saving to buy something, but in his "saving" box there is $0! I figure as he gets older, and his wants get bigger, then the "saving" box will become more used.
We also have stopped buying unnecessaries for him (except for special occasions) so if we do give him a toy/game, "just because," it is our gift to him. It has completely eliminated "will you buy this for me?!," it has given him power to make his own choices, and helped him understand the concept of money and how to use this tool (money) in our society.