What would be the best gearing for mountain climbing? I'm 59, 5'11", 210,and have had a triple bypass. I moved from the flats to the hills, and I want to ride again, but I can't with the gearing I have now. 50/34 chain ring and an 11 speed 10-25 cassette. These hills are really steep, I'm talking "Climb to Kaiser" steep, and I do not like having to get off my bike and finish walking to the top of the hill. Keeping it a double, what groupset would give me the best range and lowest gears for climbing?
What parts are you willing to replace? 

You can't get smaller than 34 in the front w/o replacing the crankset with some kind of MTB crank. You'll likely need to replace your front derailleur as well, and there are issues with indexed shifting that you'll need to figure out. 

You can't get larger than at most 32t in the back w/o replacing the rear derailleur with an MTB version. There are also indexing issues between road/MTB derailleurs. If you get a road extended cage or triple rear derailluer, you can probably make an MTB 11-32 cluster work with your current shifters. 

However, in the long run it's probably cheaper just to get a triple chainring on the front.
You'll have a much easier time getting the gears that work for you.