It is fine to want space. You may need it as you were in a very long marriage and you have a lot of other things going on in your life.

I think a therapist could be of benefit to you. To process the end of your marriage and help you cope with everything you are dealing right now. I think this will give you relief, insight and clarity as to whether you want to remarry ... and if so, how you'll know when you are ready.

My intuition says that his having three children might be an issue for you. And that's ok. Depending on their ages and how much time/custody he has of his kids will undoubtedly have an impact on your relationship. It might be a positive thing. Or, it might not. Three children makes for a busy household, they at times will be the focus of the household and you may not want to be parenting again (if you have grown children of your own). Disregard this if I'm mistaken. Good luck.