You already have the right idea. Now, should you ever get to camp at a full hookup site, you can run your waste directly into the campground sewer connection, just like the big users using an adapter like this. Drain Adapter for Gray Water, Bulk - Valterra.com | Valterra.com
HOWEVER, if you have a direct drain from the sink, horrible, noxious odors from the sewer can come into your camper through the hose because there is no liquid/P trap to stop them. I am not sure how to stop that from happening. Further investigation is in order.