We have an iMac and an iPad: sharing some (but no necessarily all) photos between the two

I am running Yosemite 10.10 4 on my iMac and my wife has IOS 8.4 on her iPad. We have over 10,000 photos on the Mac and backed up to the cloud. We had a problem in that I would load photos from my camera onto the iMac and then edit them (mainly re-orientation) but the iPad would only record the basic photo (ie before it was edited so she had to do that step again). We asked at the local Apple store and were told that she needed to switch on iCloud Drive and Photos. She did, with the result that her iPad is now swamped with 10,500 photos, most of which she does not want. Presumably because of this, her iPad is now staggering along, unable to respond in anything like the time that it did before this change.

What she wants is to have the most recent pics, edited by me on the iMac.........and to have her iPad working as efficiently as before.

If we turn off "iCloud Drive" do we stand a risk of losing the pics on the cloud?

Any ideas would be very much welcomed.