I play guitar and drums.
I think you would gain immensely from your piano playing. The joy of playing guitar is the lack of rules compared to other instruments. I learnt all the notes, scales etc but swiftly forgot them after I was old enough to drink however I just "know" what notes to play but I couldn't tell you what they are. Just embrace the randomness
As for drums. I just sat behind them one day and could play. I don't want to sound big headed but I think if you have good rhythm you can play drums to a basic level easily after that you can practise the bits needed to be a proper drummer.