you have to set up a household account online. then, any member of the "household" (i believe up to six people) can use the combined pooled miles. you cannot use them to book a ticket for someone who is not listed as a household member. If you want to book a ticket for your kids, you will need to set them up as BA members and add them to the "household".
It is time consuming but can be done online. I was able to add each of my kids using my one email address. Probably took about an hour between setting up the BA accounts and adding them as part of the household.
Once it is setup you are good to go... there is no transfer done between accounts so it is immediate.
