What are the ages of your kids? I found that I have relocated internationally -- on my own, with my DH before kids, and then with kids in elementary school/ preschool.
The hardest was the school and being worried to the extreme about my kids settling in, my needing to learn how the school system worked, etc. If you plan to be at home with them for a while, that is a great idea, it will help (you, mom and dad) adjust.
Waterloo is terrific, all the young families want to live there because it is pretty and cheap, and a lot of new energy with the in-migration to the area. I think you will make friends quickly, be certain to just ask for playdates, then invite other parents over for dinner. If you are at all churchy, try to attend a few different ones a few times each. KW is not intensely religious, many just go as a community activity and means of gaining a network of friends. Also, I recommend getting a part time job after about 6 months (or less) to meet more people.
The next hardest parts for us was 1) DH not being able to work for a while because waiting for all the paperwork, and as a SAHD, not too many other moms at school drop off would chat with him.. he started isolating. 2) Figuring out the new work / neighborhood culture. It was more different (nice, but different) than I thought it would be. For example, my work involved longer hours than I had realized it would, people around us were not frugal so we were always a bit strange to them (we drove a 7 year old minivan, by far the oldest car on the lot).
Technical challenges were building a credit rating from nothing and learning how mortgages actually worked in the new country, how taxes worked, etc.