My kids both started getting an allowance at age 6. We do allowance a bit differently, however. The kids each get their age in dollars each week but are paid every two weeks on DHs payday. DD12 gets $12 per week and DS9 gets $9 per week. They get their allowance in a check and must take that check to the bank. At the bank they must deposit their entire check into their savings account and then may take up to 1/2 of it back as spending money. I don't think that there has been a week when they haven't taken the full 1/2 back.

They each have a money box and in it are twp envelopes, along with their bankbooks. One envelope says "Invest" and one says "Donate". Each time they get their allowance they must put at least $1 in each of these envelopes. They may use their "Donate" funds toward any charity they choose. They may use their "Invest" funds toward any investment they choose. So far they have each made stock purchases and donated to several charities.
Anyway, we do it this way because we want to encourage them to save their money. Each time we go to the bank I have them take note of the balance in their accounts. Aside from the minimal interest they've received this amount reflects the same amount they have spent over the years. DD is up to more than $1000 in her account now. Our method will also give them a decent bank balance when they go off on their own someday.
We don't tie their allowance to chores or household duties as we feel those are done simply because you are part of a family. If they offer to do any extra jobs around the house we will sometimes pay them a minimal amount for that. I have, on occasion, withheld my DDs allowance because she wasn't doing her part around the house but once she got back on track she was able to reclaim that cash.
The money that the kids have left can be spent on anything they choose. I have, occasionally, indicated that I didn't think that a purchase was a wise choice, but I do leave it up to them.
I know this all sounds very involved but its really an easy system once it gets rolling. We chose to do allowance this way so the kids would have an understanding of how to handle their money.