Most things on those two bikes can be taken apart with a set of box wrenches, or maybe a crescent wrench since they likely have a mix of metric and SAE sizes.

If you've never done it before the cranks look like they need a special tool to take them apart, but they usually don't. Look online for how the lock ring comes off and then it's pretty obvious from there.

If you want to remove the gears from the rear wheel you will need to find the correct freewheel tool. I suggest going to a local co-op or bike shop since this tool is not usable for anything else, you might need two different ones, and if you try to order it from the internet there is a significant chance you will order the wrong tool on your first try. Many local bike shops will break the freewheel loose for free because it only takes a minute if you know what you're doing (and it isn't too rusted in place).

If you want to true the wheels or replace spokes you need a spoke wrench. You can get one that handles multiple sizes pretty cheap. But if you're doing more than simple adjustments you probably need a truing stand. Again, local bike shop or co-op is your best bet.