I have done such a trip (only with 4 boys) and rented a MN 4.  It is a barge but is sufficient to the task of travel.  It weather-veins and it can be difficult to keep it on track in the wind but I had a 15yr old in the bow.  It's impossible to fish out of when it is empty.  So, if you're just traveling and hauling gear from place to place I think you will find it sufficient.  Can the 10 year old kayak alongside maybe?