You need them for the wheel bearings, and they need to be the super thin (1.5mm thick) wrenches. Also a regular wrench used on the pedals usually results in scratched cranks. A proper pedal wrench is also very thin.

I would look at the Parktools site. Some of the large sets will contain things that most home mechanics rarely use. They are meant for professionals. The smaller kits like the roll up toolkit are great for a basic set, and may be a good starting point. You will, like Syndney said, need some different things for the older bikes.

Of course if you going to have a fleet of bikes, one of the larger sets may be what you need.