I'm always fixing stuff, so when I came across your tools, I ordered the Pro Tech Base Toolkit. Just so happened that the day after it arrived, my son asked me to help him change the battery in a GameBoy cartridge.
Unfortunately the your set didn't include the tip needed to get the screw out (we used needle nose pliers). We did get to use one of the metal spudgers to pry off the battery leads. It was strong enough and did the job nicely without breaking the contact strips.
Make sure you keep the spudger flat against the battery when prying off the contacts so they don't break.