I dont think anyone can tell you what to do...
Only you know what is right, both for your family and yourself. You are obviously unhappy with your marriage, and now you have met someone you probably feel that its the right thing to do, its nice to have someone out there that can take away the unhappiness of your marriage, but how well do you really know this other person? You say nothing has happened yet? Im sure you do feel some love towards him and him you... Is he married too? But do you know this person really well, or are you just seeing the surface of him if you know what i mean. By all means, if you feel its the right thing to do, then you have to go with your heart, but im not sure leaving your husband and getting straight heavily involved with this other guy always works... You need to take the new relationship slowly... and leave your husband because you want to , not because you have someone else out there.
Would you have thoughts on leaving your husband if this other guy wasnt there? Thats what you need to ask yourself, or would you just accept that things arent right and just carry on with life at home.
Its very easy to follow your heart and feel that you want to be with this new man, but ensure you know him really well, and take your children into consideration. You need to be given a fair chance with him to know if its the right choice.
What does he think of your children, do they get on well together? Has he even met them yet?
A new relatiosnhip is always very different when its just the two of you, to when there is a family involved....
Its not an easy decision......
but i hope you make the right one and will be happy...
good luck x