It never hurts to make a new friend but I hope you take it slowly. Just the fact that there are red flags concerning the kids is a caution sign. Talk to him and explain how you are still healing from your past relationship and would like to get to know HIM better before dragging the kids into it. Especially for the kids - it's not healthy for them to have people floating in and out of their lives either. If he's not willing to do that then I think you already know what you should do.