Why would you need a check valve? Many have metal springs in them and can rust over time. The drain doesn't need a check valve, unless gravity fails (in which case there are bigger issues), and a siphon break (a small hole drilled below the water line) eliminates the need for one on the return.
Otherwise it looks good, just make sure you can access and fully turn the ball valves.
One suggestion I would consider is adding an outlet for expansion. simply add a T and use a cap or a ball valve at the end. If you choose to create a manifold or want a water change drain later, it becomes much easier to add it on.