Welcome to AA and to the hobby! It's really not that complicated. It does make sense that there should be a good environment for fish since they do everything in their water from swimming and playing to eating and pooping. Once you get it established it's very enjoyable and relatively easy to maintain.
Since you already have fish, you might consider doing a fish-in cycle rather than the fishless. I don't know how old your daughter is, but if she is young, she may not understand and will want to keep the fish.
Fish in cycle can be somewhat stressful on the fish, but I think as long as you keep the ammonia and nitrite levels bearable, it'll be just fine.