I'd go with something else for two reasons. The more concrete is that mineral oil will evaporate over time. The other is that various keyboard folk have spent lots of time with lubricants and have never ended up at mineral oil, which is easy to acquire and seems like an obvious pick if it worked well.
Most will recommend a mix of krytox grease and oil (I use GPL 205 and 103), but I'd recommend buying a premixed kit from a keyboard site. I believe techkeys.us sells it, as does zealpc.net.