I have an 2008 Odyssey. Soon to be five children all of which are 40lbs and less. Five and Under are their ages.
We fit three 2009 manufactured Sunshine Kids Radian65 in the 3rd row. They fit beautifully and plus some room to fit a few books in between the seats. Especially for the one in the middle. Max weight is 65 lbs. Minimum is 5lbs.
Pros:
They are kid friendly: Independently buckle themselves. Parent friendly: Sometimes my 3 yr old has to have help. I can do it with one hand reaching back. It can be rear-facing for the littler kids. They can be folded and taken on airplanes. They are not bulky. No armrests or cupholders or funny pillowlike things. They do not expire for 8 years (most are 6). Which is a perk, b/c you really could just buy this after the typical bucket/infant seat and stick with it until they are able to use the car belt. I find that the five point harness is okay if your child isn't going to be very tall by later ages, meaning 6-8 yrs old. The simple lines and three in a row in the back, look just like a bench seat. So, if your child is feeling a little embarrassed to be in a carseat... It really doesn't look like one. We have grey interior and bought 3 of the same grey/black carseats. Also, when fitting 3 across, it could be difficult to latch the Honda carseat belt with carseats so close together. We have found 18 inches too wide for a carseat. These are 17 inches wide with little belling out on the shoulders. Some manufacturers don't always tell you the widest part.
Cons: They are expensive seats. I was able to buy 3 in September for 180/each no tax charges, online with the bonus carry cases. They are about 225 Average. But, if you price buying possibly 4 levels: Bucket, Convertible, 5 point harness, booster. The last 3 levels could be about 200 per child.
I am a big fan of this van. In the second row of the van is a bucket seat (flush to the door) and a convertible(in the middle position). This allows for two sides entry/exit for the 3rd row passengers. I have to take out the bucket seat before using that easy lever to fold the back of the honda seat forward. The base stays in.
I am no expert, but sometimes going through many options that work and doesn't work really make you appreciate when it all comes together. Hope this helps.