I'm not sure why it is a bad thing for a restaurant to cater to an adult audience? They probably should make it clear when they take reservations that families with children will be seated in the lower area. If you don't like it, don't go there.
As to whether children are "well behaved", all parents seem to think their little darlings are "well behaved". Can you imagine a restaurant trying to sort out the naughty or nice children? Yipes! (This may be one reason Santa lives at the North Pole, far away from angry parents) As one person stated, how could you possibly know until well into the meal. Then if they are NOT well behaved are you going to banish the group to downstairs? OMG
There would be restaurant rage.
If you want a to eat in an adult atmosphere, get a sitter and enjoy your night out. If the kids must be with you, go to one of the numerous family venues around the lake.
Having said all that, I rarely eat at Canoe. The meals are mostly fine but quite pricey, IMO.