Son is going snow tubing w/ Cub scouts...?

Snowboarding pants would work fine as long as they are insulated well enough for the temperatures that you're expecting. One issue with snowboarding pants is that they can be built for style more than warmth. If the pair you've found turns out to be not well enough insulated have your son wear an extra pair of long johns or poly/cotton fleece pants with them.

Since snowboarding pants don't go above the waste line like bibs do it can be easier to take in snow while tumbling around. Nothing feels more chilly than snow finding its way under the coat and into contact with the skin around the waist, ribs, lower back etc. If your son wears a long sweater, like a hockey jersey, tucked into the snowboard pants it will help keep him warm and help keep the snow out and off his body when he tumbles around in the snow.

CCS catalog has great deals online and in the catalog.. I recommend online if it's in the next 2-3 weeks though..

Other than that Snowboarding pants are the best deal..

They are on clearance at Wal-Mart and K-Mart. I was just in there on Saturday. I'm sure your local store should still have some left.