We have a Suburban with a bench 2nd row so I'm adding a few pros/cons that I see. However, we only have one car seat now with a second on the way, so a little different situation.
The reason we went with a bench is there are times when we get together with frinds or family and we do need to get 8 people in a vehicle to go somewhere versus 7 you can get in with captains chairs.
One thing I did notice is that there are only 2 sets of LATCH hooks for car seats in the 2nd row bench in our Suburban, so to put a third one in would require using the seat belt to secure it. (Not sure if this varies at all between models or years, so something to look for.)
If you don't need that 8th spot for someone periodically, in your situation, I'd probably lean towards the captains chairs. If you would have use for getting an 8th person in once in awhile, I'd consider the bench.
Or... if you have a use for the Suburban where it would come in handy to take out the back seat, I'd go with the bench 2nd row. Then you still have room for the 3 kids. When we go camping, we have taken out the back - and that's just with one child. (I don't want to know what the pile of stuff will look like with another one next summer! :)