A.M.
Hello. We have the same 2005 Jeep, and we don't have 3 in the back, we have 2 (1 infant, 1 convertible) and I am still able to comfortably sit in the back middle when the kids are fussy. I'm really not thin either, a little heavier than average since I just had my baby. So, I would think as long as the convertible car seats aren't too wide, it should work. A little crowded, but should be fine. Good luck!