Hi G.,
I may have an unusual way of looking at things in this department. My husband and I don't like the idea of allowance for the sake of allowance. And we don't like the idea that we pay our kids to do a few basic things they should do, as a part of the family. So, we've created a system where they do chores (duty) and also have the opportunity to earn as much as they'd like to earn. It's a little harder to keep track of this, but it seems to work pretty well, overall.
Basically, we have included chores from the time our children were about 3 and look at chores as unworthy of reward or payment. We tell them it's because they are a part of a family that they have certain things we expect they do each day, just like we do. If they fail to do their chores, it impacts the whole family (we want to instill this understanding that there are things we do not because we get a reward but, because we exist and co-exist, we must).
It doesn't have to be a ton of work put on them - it just has to be work that is theirs and consistent and expected. Because, as it is with adults, it doesn't matter what the job is, a job well done offers its own reward of personal satisfaction and contribution (and, for children, a growing sense of self esteem is a great thing to nurture).
Beyond that, we offer a list of jobs, each with an amount they can earn. If they want to earn money, they can do as much work to earn as much money as they would like to earn. It's interesting - sometimes they decide to do a lot, usually after we've been to the grocery and they've asked for something like a pack of gum, to which I've responded, "can you afford some gum? If not, you need to do some jobs so the next time we come to the store, you can buy some gum."
We figure, in life, there's always stuff you have to do, whether you want to or not. And, in life, if you want more than the basics, you have to get to work for yourself. So far, it's a good system, although, like you, I sometimes battle the consistency factor (time management with all the things we do as moms these days!).
The other thing that has come up is that it takes a lot of time for them to generate a good amount of money - it's not all instantly given. So we created banks for them and are coaching them on what to keep in and what to take out, so the whole discussion of money management is there, as well. But we allow them to make the choice - it's their money. If they want to blow it all, then that's it. It's gone. If not, they may be able to use it at a critical time. They have all saved and saved well, on their own. A fun thing I remember hearing and have shared with them is the story of that long-term study they did on the "marshmallow test" - did you ever hear that? A researcher sat in a room with a child where there was a hidden camera, a small table, two chairs and a phone on the table. Just after they said hello, the phone rang - the researcher answers, says "okay - be there in a minute" and hangs up. She (researcher) tells the child, "I've got to leave the room for five minutes - I'm going to give you this marshmallow. If you don't eat it, I'll give you another when I return. If you eat it, that's it - you only get the one." She leaves and the camera captures the children - some sitting there, just waiting; some "pretending" to eat; some nibbling and hoping it won't be noticed; some chowing down! Apparently, they followed the group of children into their adult lives and determined, the children that held out for that second marshamallow were clearly more successful in life than the group of those that did not. It's fun to tell this story to children - kids are so smart! They totally get it.
Anyway - hope it helps in your process of pondering this - I think it's great you're doing critical thinking on this, btw. It's easy to slap down allowance at a certain age and not really think about what you want to achieve for their overall character in life. But YOU are really thinking about what's important for you to instill, as a mom. And that's worthy of a great deal of respect in my book. I hope you know that you're teaching them, in the process, how to think things out - and that is hugely critical. I fear we are leaving our children with more problems than were left to us - and believe teaching them how to think critically and problem solve for themselves is a life skill they are going to need even more than we do! So good for you, G.! You're the best kind of teacher for your children.