"mike and amy" First, I am sure you are going to be happy with your Bennington if thats what you decide on. As for the motor, I have a Yamaha 90 on my 2275 GFi and already wish I had gone bigger to the 115hp. I suggest you go with the biggest motor (hp) you can afford (and be liberal about what you can afford, lol). When I was shopping all different kinds of pontoon manufacturers last year, various dealers would always say I could pull tubes "with ease" regardless of the size of the motor they were trying to sell with the pontoon. I consider myself lucky I didn't settle on a 40hp motor.
As for the size of the swim deck, mine looks to be only 2/3 the width of your model, but I now consider it essential. If for no other reasons, it is a great place for my 10 year old grandson to "drip dry" for a couple seconds before he comes into the playpen area. I suspect with two boys, you will come to the same conclusion. Plus it is a great place to install a grill on a pedestal as some others on this site have done. Since I trailer my boat also, I find it is a great place to load stuff on the boat from the house (like full coolers, food containers, toys, my portable jump battery, etc.) then I only have to climb up once to move the stuff to various locations within the playpen area.