I have two adult daughter and neither of them... have Crohns. I watch them like a hawk too!
Looking back at raising them there were many times I was in a flare. Didn't get dx until I was 36. I would get very fatigued and didn't really get alot of help in raising them during those years because my husband and I both worked with not alot of family support.
I suggest absolutley having children. But, know that you'll need help now and then. If your family is supportive and willing to help out children are the best thing about a family. Worrying about passing something down is the risk you take for the Love of all time. Even if a Dr. said your chances are 0% ...a baby could be born with a heart deffect and you'd Love it all the same.
I have Crohns and my Brother has MS (Mulitple Sclerosis) both auto-immune. When asking my Dr. about the chances of me passing it down to my daughters he said 5%.
But, I do believe that getting an auto-immune is somewhat of a "melting pot" I believe it is situational, viruses, stress, yada yada mixed with the genes passed down.... Putting a real finger on WHY we get it actually hasn't been discovered yet. If it was we'd be cured!
I do know this about auto-immune. USually, usually getting pregnant a person goes into remission. not always but usually. Your body is going to do everything in its power to create a healthy baby. Now, afterwards....if your run down or have had to have a C-section...you could flare. Surgery can also cause a flare with auto-immune. This is why many Dr.'s just run antibiodicts after surgery with a dose of pred.