"can you see yourself married with children? I'd like that eventually and do think it's important to be up-front with someone I'm seeing beyond the first few dates in case it's not in their life plan"
This is the crucial question really. I think you should ask this first and then see what he says. At 40 you haven't got time to waste on someone who does not want children.
I very much doubt he would want children at 50 living the lifestyle he has now. Children would make a huge difference and he'd be facing 20 years of bringing them up with you and having to make sacrifices to his lifestyle. There's a remote chance he might want to do that and be prepared to give up activities etc. to bring up children but I'd be very very careful OP. You wouldn't want to marry him, have children and then he starts getting resentful because there's been an enormous change to the lifestyle he's become accustomed to over the last decade or so.
If he says he does want children, the next thing is to establish why he hasn't had them before he was 50. Yes, it sounds awful, poking your nose into his past and his business, but I think it is important to know. (I'm assuming from your post he doesn't have children already as you don't mention them, but perhaps he does). Men who want children normally have them long before they are 50.
You also need to know a bit about his relationship history. I'm very wary of cocklodgers having had bad experiences with 2 of them, so maybe I have become paranoid. Not all men are cocklodgers!! But, if he's got a history of moving from woman to woman, usually successful women with their own properties, then you need to be very careful. That's different to him perhaps being divorced or having a couple of long term relationships. Is part of his financial planning that he's saved a fair whack of cash but plans to top it up a bit by living with a woman who will be working for the next 25 years - a nurse with a purse - securing his financial future and making sure he has someone to care for him as he ages.
I think if it were me, and bearing in mind I'm late 40s and don't want children, I'd date him and have fun with him and see where it went.
But as you clearly want marriage and children I think you should probably throw this one back and look for someone else.