I'll expand on my one-liner about keeping everything.
So, Olympus: it has sentimental value which you should never discount. Second, it's fully manual and mechanical. There are no proprietary and obsolete electronic chips in it; there aren't complex electromechanical subsystems where each has to function always or otherwise the camera becomes a brick. It can still be maintained and kept functional for many decades to come. The lenses you already have form a good system.
Likewise, your Nikon is a time-proven good camera and lenses you have are good: solid, with good manual focus and aperture rings, infinity stops, legible scales. Yes, you could sell them - but likely you'd enjoy having and using them more. Nikon still makes the 35mm, 50mm, 105mm manual lenses (I think) just because they are so good. More expensive new now, but you already have them.
The EOS system has been a great success for Canon. I can put a new-today EF lens on the very first EOS 650, 620 bodies of 1987 and it'll work perfectly. I can put an old EF lens of 1987 on, for example, a Canon 5D MkIII and it'll work perfectly. So, I'd suggest keeping the Canon system as well - maybe add the new 50/1.8 STM. I've got an old 50/1.8 II which many say is noisy and slow, which is somewhat true, but even with my $20 Rebel G, I've had it nail some spectacular shots wide open (like a spider in a glistening web).