2 cars AND the trailer 10k?
If your layout turns out like it looks like it will, the trailer will push about 3k empty.
Then again, I don't know what you intend to do on decking, which is the part that really weighs it up and causes drag.
I think it's great that you're teaching your children to weld and build trailers! That way they can get lots of practice building them for several years before actually putting one in service on the road. Good job!:clap: