A drill with variable speeds is useful both for drilling and for setting wallboard screws.  Wallboard screws are terrific for wooden go-karts!  They're easy to set without pre-drilling, and they're very strong.  Frequently we put washers on them.  We prefer drills with cords over rechargeable ones both because you don't have to worry about dead batteries and because they're easier on the environment.

A saws-all is very versatile.  You can get metal and wood blades.  They can cut curves and reasonably straight.   They're much safer than other saws such as circular saws.