There is no way to predict if you would have fertility issues post surgery. But 25% of the regular population has fertility issues so even without surgery you could have issues.
I was unable to conceive naturally after surgery but had great success with IVF - I have an almost 9 year old and a 6 year old.
If you are close to wanting kids, the current thought process is that you should have the colon removed with a long term ileostomy. Have your kids, the complete j-pouch process. The reason is the surgery to do an ileo is far less invasive and traumatic to the I sides, so fertility risk would be lower.