Hope my perspective helps here with my kid placement in the LR3...
we now have 3: 6, 4, and 1.5yrs. The 6 yr sits on driver side 3rd row with a sideimpact type graco booster (works great!), the 1.5yr is on pass side facing rear (safest way to face for kids almost under 2 yrs and X lbs..), middle seat is folded down for pass through and 4 yr sits behind me. when #3 was born, all 3 kids sat next to each other in Britax seats of various models. they were tight but once the oldest was 5.5 yrs, he went to row 3 for more space and now in a booster. Note: adding the youngest in the middle works but over time if you have to lift them over another seat, that gets old very quick....
Now if i need more cargo space for all their bikes, trailer and stroller and/or beach gear, all 3 sits in row 2, otherwise, i keep the middle seat folded all of the time. Its a nice flow and keeps everyone separated too. all 3 like the challenge of climbing in the back and walking through to their respected seat...If the 2 extra cousins go for a ride,, yea, each seat is taken and if an 8th person shows up, they get strapped to the roof.... haha