Bike repair can be done using Allen wrenches, screwdrivers, a set of crescent wrenches. If you plan on replacing the bottom bracket or crankset, you'll need a crank puller and a bottom bracket wrench. Maybe two or three different ones depending upon the make and age of your bikes. Pedal wrenches are nice because they are much thinner than your crescent wrenches and can get into the tight spots. Might want to have a spoke wrench to tighten loose spokes. Headset wrench for threaded headsets is 32mm, usually just out of reach or most adjustable crescents and the ones that do fit are Huge. Cutting brake/shift cables requires some nice cutters, simple wire cutters from Home Depot aren't up to doing a neat job. Cutting cable housing is best done with the proper tool but you can also use a Dremel cut-off wheel to do a neat job without mashing the housing flat. Don't forget to ream out the hole before inserting cable.
If you need to replace a cassette you'll want a chain whip and a lockring remover.
Park Tools has a very nice website with lots of "How to" instructions if you get stuck on a repair.