Well me personally, I wouldn't. You may not be officially dating, but neither are you officially just friends, and one way or another there is going to be a lot of speculation.
I think you should meet the kids away from this event - they are going to feel out of place too with Daddy's new friend there, and in my opinion, the whole relationship - if you want one - is better if you take it bits at a time. Having been in a similar situation once, I'd go out on a family day out, just you, him and the kids.
PS, I wouldn't worry about the age gap - sounds just right to me.