I wouldn't unless you really believe he'll quit or unless you have lots of money to spare. It is rare for anyone to go into rehab once, kick it and be done with it. Often they just walk out and we're out our retirement money. Jail may knock some sense into him, but there is no guarantee. Addiction is powerful. I'd send him to the one on your insurance, if he is willing to go. When my daughter quit, she quit because she wanted to quit. She was doing meth and psychedelics and cocaine and was snorting crushed up ADHD medication too, which is a common drug for users to snort. We never sent her to rehab and had no idea how bad it was until after she quit. We thought it was just pot. Almost all parents think that at first, because, as I know, it is too horrifying to think it is anything more.
Being a realist (or a cynic as my difficult child says), I think he will need time before he is ready to turn it around and you need your own life too. Looks like you have three kids and a grandchild. Is it fair to invest all your time and emotion in one adult child who is messing up and letting the people who love you and are doing well to be slighted? I don't think so. difficult children tend to suck the air out of our worlds, then, when the dust settles, they tend to stay the same for very long periods of time and we look up and see we have wasted years that could have been better spent with our respectful, law abiding loved ones and being good to ourselves. We count too. Yes, I thought that was terribly selfish the first time I heard it. But it's true. You can't change your son. Only he can do that. Rehab can't change him. Only he can, if he's ready to do it. Heroin is not easy to kick.
My daughter quit in a basement with her boyfriend and didn't tell us she was quitting in case she failed. It has been over ten years. Proof that people will quit when they want to quit. We would have sent her to rehab, but we had no idea how bad it was and I don't think she would have ever gone.
I do hope your son gets to go to rehab instead of jail because I do think he deserves a chance to prove he can be a different and better person. So crossing fingers, eyes and toes!!! In the meantime, remember that other people need you too, including yourself. Be good to you and don't spend every moment thinking about your son. It won't change anything to ruminate about him. I wish somebody would have told me that earlier. Seriously, I superstitiously used to think that if I didn't dwell over a problem, it would persist. The fact is, it persists or doesn't regardless of dwelling on it. We have no control over anyone but ourselves. All you can do is wait and see. Jail has helped at least one difficult child on this forum think hard and change her life. Jail isn't all bad.