Help with insuring 18 year old

We live in NY state and my 18 year old son will be no longer eligible for Child Health Plus early next year when he turns 19. I’m trying to determine the best and most economical way to cover him for the next couple of years until he gets his own insurance through work.

I have four different Excellus plans available through my employer, but have not used those because I go to the VA for my healthcare and my kids have been covered by CHP. A HDHP 6000/12000 plan would cost about $1200/year, while a HDHP 3000/6000 would be about twice that. Since my son is only 18 and healthy, I’m thinking we’d get a cheaper option that would mostly be in case something catastrophic happens.

I’m also looking into the ACA, but am a little unclear about the income requirements, since we live in the same household. If they factor in my income ($130k/year) there would be a huge difference in costs compared to just using my son’s (~$20k). 

Any suggestions or clarification would be greatly appreciated.