I'd go with Canon if you want a future for your gear. Olympus has discontinued its whole slr line, so while it would be cheap to buy a couple lenses (maybe secondhand) now, you'll be pretty much stuck down the road.
Re wide angles, a 24 is a fine lens you'll keep using in the future. For your use, I would also consider a wide angle zoom in the 20-35 range, you can find a couple not very expensive ones under the Tamron and Sigma lines. Keep in mind you'll find superwides more difficult to compose with if you have no foreground interest, and flare can be a problem sometimes.
Finally, don't forget a good polarizer. Make sure it does not have a greenish cast (very frequent in cheap ones), and that it won't produce vignetting with your widest lenses. If you need, buy the biggest diameter you'll need and a step-down ring to use with the others.
Good luck on your trip!