Yes I want to know what you mean by Booster.
Booster to me is:
http://TRUS.imageg.net/graphics/product_images/pTRU1-6937820dt.jpg
I own this for my 6 almost 7 YO Nephew who weighs 45 LBS, he transitioned to this at age 6 per his mother, I disagree but it is the seat she says is fine for HER child whom I pick up from school because I am active in his life and my Job affords me the ability to pick him up and care for him until his mother comes to get him a few days of the week.
My daughter who will be 4 very very soon is in this for a few more years because it will be fine and safer at the maximum of 65 LBS. "Safety 1st, Complete Air"
http://ecx.images-amazon.com/images/I/410fSKZ1q4L.jpg
My 6 Year old nephew above will move to the front seat of the STi because my Son will be born in 5-6 weeks and will be in the backseat, the Airbag will only arm and be on if there is 90LBS in the seat.
If you cannot turn the airbag off in the front seat, your child should not ride in the front seat period. Remember you can talk about how safe you are going to be, and your route, but others actions are not in line with yours. You can be proactive about your child's safety, however you cannot control others actions. I don't like my nephew to be in the front seat, but with 2 Car seats in the back there is not room for him in the back unless he sits without a booster, and To be honest I am kicking that idea around. Why? Because of this research and video (Starts Slow and is long but Good IMO) and the stuff Greg posted above my post: