I personally have a Chevrolet Tahoe and could EASILY fit 3 across. I prefer to keep my kiddo harnessed past that 4 year/40lbs mark as it is one of the safest ways for a child to travel. I do have 2
Britax Regents outboard with ZERO room in the middle for another seat (I even tried a Scenera
RFing...no go). Now, with 2 RA's and a
booster? I bet you can get 3 across easily. We have had our Tahoe for 4 years and really enjoy it. It also has an optional 3rd row.
My advice is to purchase the next seat that you are wanting for your daughter, take the 2 RA's and put them in vehicles that you really like. I highly recommend keeping her in a harnessed seat much longer, but 4 years and 40lbs is the minimum safety standards (for recommendations, please refer to the
convertible seat section of the forum).