Son is going to elope

So my 30 year old son has told me that he is going to elope with a girl who he’s been dating for 6 months. He’s has been through a divorce already due to a failed polyamorous marriage and he was devastated almost suicidal from it. He’s been dating a woman who is a recovering alcoholic who has 2 kids and she’s been good for him and they seem very happy together. He’s currently unemployed and currently lives with my ex wife. He told me yesterday that they are going to get married in May. I’m not sure what the current situation is with her child custody situation is but she seems very nice and seems to love him very much. How do tell him that I think he’s moving to fast without not sounding unsupportive of him? He’s had a history of jumping in too deep and too fast and he’s been in a very happy place with her. But since I don’t live with him anymore I don’t know the circumstances of her child custody situation and I don’t want to come across as not liking her, I just don’t know a lot about her and her situation. And as you know when you we point out things we seem to get the “don’t you think I don’t know this” attitude. To me it’s just “what’s the rush?” And when he was in a dark place I told him “you hit rock bottom so put down the shovel “ now I m like just because you see so light doesn’t mean that you’re out of the hole! How do I handle this?