QuasarJoke
Everything @N1b said is right on point. Most important of all is the point he made about not pushing privacy and security too much. Be very ready to sacrifice. The fact that they are on a phone without privileged google components is already a big "privacy upgrade".
A few things I'll add:
With newpipe and libretube, i couldn't get anywhere with people telling them about its privacy. However i'd tell them "look here is this youtube app replacement, it blocks all those ads (this point never impressed people enough), and allows you to download videos and watch later, AND you can just LISTEN with screen off or locked, AND allows you to just download the audio for when on the road or no internet." And then in a very short and succinct way i would give a few examples (music, lecture presentations, podcasts they liked). As soon as they realized the implication of this and how they could "listen" to youtube videos with screen off and with less or no internet they all lined up wanting to know how to get this app. All the iphone folks were specially interested. These older folks often drive to work and want to listen to meaningful things they like from youtube, but the youtube app experience limits them. Enter newpipe. My father who cares none for privacy is now hooked on newpipe.
Another point is that graphene by default is missing some important components. Calender, photo viewer, photo editor, voice recorder, a good keyboard, a good contacts and dialer app, an audio/video player, and a maps app. You should make sure all these are in good working condition for them that makes them not even notice. If they don't even notice these that means you've done your job right.
Next i would say consider installing google's voice recorder, voice assist, camera, and photos apps for them, set them up and internet isolate them. This way not only do they have the functionality but they will be impressed with quality and bells and whistles they haven't seen before. As for keyboard, for a maybe more privacy assured option consider Microsoft Swift keyboard, and for a "maybe" more risky option (because of IPC) use Gboard.
Keyboard is important as good autocorrect and key registration is gonna affect them. Maybe even setup voice typing.
Setup a working map app and integrate it with the voice assist.
Using google maps may also be unavoidable as these folks need business info often and asking them not to use gmaps is probably a tall order. They are used to pulling phone numbers and calling immediately.
I want to suggest to install gmaps on a separate profile without play services and with a free vpn to isolate their location footprint from the rest of their google footprint, and tell them to avoid using it but do use it when they need to. But this method might be problematic for pulling phone numbers and calling as you cant copy back to main profile. So i don't know, see what you can do here. Maybe using browser instead of app might be acceptable for them.
Also get them something like ViMusic or InnerTune. Free music on their phone. Explain to them that these are some of the nice extra benefits they get by going the privacy option in compensation for some things they lose and that its a tradeoff, and for a good cause.