Why do most people wait until their children are 15-16 to make them work? I think we can still have them do small odd jobs around the house and for friends and family, and yes, they need to make some money. They need to learn to save some of it, spend some, and lastly, give some.
I also think this is different than chores around the house. I think there should be some block of time during the summer each day that, even if it is for an hour a day, they "know" they are "at work." I think them knowing they have to go to work and do a job is good for them, and they learn that they "have to work" in life. This will help teach them that no matter their age, they can improve their life/situation by going to work.
Do you remember how good it feels to work hard for something, have to save for a while, and then finally be able to get it? Then, we end up being torn with emotion on not wanting to give up our hard earned money in order to get it. Our children need to learn what that feeling is, and they need to learn how good it feels to help someone else with the money they have.
So, this summer we are handing out the jobs in our house and telling everyone to get to work, and to not forget to do their chores after work.