Don't suppose C2 will be one of the permitted engines...?
Any engine or development environment/tool is allowed this year. Construct included. They do have special prizes for "sponsoring" engines, which is indeed a bit odd, but understandable.
I think this is a good opportunity to showcase Construct as well. The game art packs included in the Humble Bundle deal can be used with any game dev tool and environment as well. And Spriter is included, which works really well together with Construct (and sort-of with the included App Kit 2).