Not crazy at all, it's the smart thing to do You can download a blank home contents calculator off most of the insurance websites to give you a start. That's how we got started. When we first did this (which is when we bought our house 4 years ago) we went through every room and valued all the items. It's surprising the amount of things you wouldn't normally insure unless you open every cupboard. Perfume, household electrical items (blender, food processor, vacuum cleaner etc).
When we had DD1, we did it all over again as there were quite a few new items and we wanted to also make sure the value we put on items was still reasonable.