I predict you will need to empty that small bucket pretty often. Once it get much more than half full, it will start sucking dust into your shop vac's filter, making it useless pretty fast. Consider going to a bigger chip collector, 30 gallons is good.
And, add a Dust Deputy to the top. It uses 2.5 inch hoses and will dramatically decrease dust getting to the shop vac. The Dust Deputy is going for about $50, a good quality drum will cost anywhere from $20 bucks up. You can use a metal trash can, but will have to cut an opening in and probably reinforce the lid. A plastic trash barrel will definitely require a reinforced lid, and you'll need to line the connection between lid and can with some kind of gasket and several bungee cords to keep the lid down. Some folks replace the plastic lid with a shop made one of plywood. Not a bad idea. I'm a fan of the Harbor Freight dust collection unit when it is on sale and you have a coupon--about $170 or so. But the shop vac might do what you want since you have the dust attachment with brush for your CNC. Worth a shot.
The more I do, the less I accomplish.