I'm not technically-minded at all and only know what feels right for me.
I can understand the dilemma if you're considering whether to suffer the expense and trouble of going from two chainrings to three. But if you've already got three, and the ten speed is compatible, I can't see any value in short-changing yourself. Are you hoping to save weight or make the gearing set-up simpler? I must be missing something here. Perhaps I am in over-my-head commenting... It just seems like taking the light bulbs out of your car's head and taillights because you aren't planning on driving at night
If you've got a burning desire to change something in preparation for the trip, buy a better saddle, upgrade the tyres or something else that will be useful!