We did the floatplane through
DCL last year with our 7 and 4 year old. The seats are small and can only fit one person. As someone else posted, there are single seats across the aisle from each other. There are a few seats at the back of the plane that are 2-3 wide (sorry, I can't remember the exact number). The flight was fine for adults - beautiful scenery and informative narration - but the kids HATED it. The plane was very loud, very bouncy with sudden drops in the altitude and scary for them. Every child is different so only you can be the judge of whether your 2 year old would be ok on the floatplane. Keep in mind that you most likely won't be able to have a child in your lap and you will have to/need to stay buckled during the trip because of turbulence. In hindsight, we would have skipped the floatplane excursion for a couple of years and picked something else. It was expensive and not fun with terrified kids on board. Unfortunately, we didn't anticipate any problems because the excursion description didn't allude to any of this. HTH.