Here is my 2 1/2 year old in a forward facing car seat and my 4 1/2 year old in a booster seat. Last year they were both in forward facing car seats. No problem for them to climb in and out of the back seat. The passenger seat extenders are a must have so I can climb back there and get them buckled in.
That's awesome, thanks a lot for the pic. I have a 19 month old and a 2 month old but it looks like two bulky car seats would fit no problem.