Edited by Alpenglow - 7/9/13 at 8:08am
I would probably get a Turbobooster for the SUV if you feel your oldest child is ready for it. But really only you can make that decision about whether a booster is an appropriate choice.
What ages/sizes of kids do you need to transport in the Focus?
Do you guys have the Ride Safer Travel Vest or the Bubble Bum up there in Canada?
The RSTV and Bubble Bum are what's called "portable" booster seats. What I meant earlier (but didn't ask clearly) was what the age/size of the "occasional" kids you'll have in your car when you need to squeeze in 3-across. The Bubble Bum and RSTV are both very narrow and will fit where no other car seat or booster can be squeezed in. BUT... they'd be more for your older kid's friends who are booster age, not for younger kids you might be babysitting. And I don't know whether they're approved in Canada.
They're handy for what they're for, but I wouldn't want to use either one on a daily basis. Neither one is likely to be able to be buckled in by a child and they'd probably both need an adult's help.
(Shown here with lap belt and top tether)