Anything less than 13' is getting pretty short for a 6' 2" adult weighing 225 lb. I have seen adults in 13'6" canoes and they are much less suitable for adults than a 15' canoe, especially if you want a big safety margin in stability. My experience has been that while a 13'6" canoes is a good size for 10 to 15 year old children, two children with a 15' canoe is a better idea than two adults in a 13'6" canoe.

As you make the canoe shorter, it need to be wider to maintain both the volume and the stability. It can get wide enough that handling it on the land and on the water becomes difficult.

The longer canoe will be more efficient and more enjoyable to paddle, but I am thinking more of the safety with the 3 yr old granddaughter.

If possible, it might be a good idea to try to spend some time in a 14' or 15' canoe and a 12' canoe and see if you agree with me.