Technically, "best practice" is that the least protected child is the one who should be in the safest seating position. Odd as it may seem, rear-facing carseats provide the most protection from side impacts. So, when given a choice, the front-facing child would be in the center, and the rear-facing child outboard.
An even better arrangement would be to have one in the second row chair moved to the center, and the other in the center of the rear seat, though that is less convenient.
Personally, I have my 17 month old and 3 year old in the second row chairs, both outboard. There's still quite a bit of room between the chairs and sliding doors (more than most cars), and the Odyssey has reasonable side impact protection.
Just make sure your carseats are installed properly, and that is the most important thing you can do for your children's safety.