You can fit a Frontier and two True Fits in a 3 across?
Wow!
If you can fit it, and it's suitable for your child, the True Fit Premier is on sale at Zellers this week for $120, which is an amazing deal.
This is for the youngest child? As you probably know the TF rear faces to 35lbs, which for many kids is more than enough, and of course it's quite tall.
With the selection of seats you have, would it make more sense to pass the Frontier down to the middle kid, the True Fit down to the littlest one, and get a new booster for the oldest? If your oldest is ok in a booster full time, that is. For long trips you could always swap seats around and put her back in a Frontier. Just throwing that out there in case you hadn't considered it...