This is right up my alley, both wife and I have been "degoogled" for a few years. She's on the microG build of LineageOS. My old phone died, so I just got a new Pixel and switched to CalyxOS. Its been fantastic so far, comes with MicroG built in, most stuff "just works" without any advanced tech knowledge needed. FDroid for open source apps, Aurora Store for downloading anonymously from Google Play for the few apps I need that aren't open source. I've had no problem using the apps from a very large US bank, nor from a very large US investment bank. Other non-open source apps like Garmin Catalyst, SpeedHive, etc work just fine as well. You just want to limit how many you use, as most closed source apps are privacy nightmares.
Ironically, the Google Pixel line is the most supported with aftermarket OSs, I'd just buy a used one and switch, save yourself the hassle.
I use Kagi for search. Its a paid option, buy works great. Unfortunately, everything else starts to require more and more tech abilities...
Fastmail (paid) for email, and your own domain name so you can switch providers easily if needed. FairEmail for Android email client, FastMail's web client on desktop.
I use Nextcloud on my own server for file storage/backup. This replaces Google Drive. The phone app will auto-upload pics and video. PhotoPrism to replace Google Photos. Nextcloud with Davx5 on the phones to handle contact and calendar syncing.
A nextcloud app called PhoneTrack along with the app of the same name on the phones to replace Google Maps location history/sharing.
Aegis for open source 2FA. Keepass file stored on Nextcloud with open source clients on devices for password management. There's an open source app called SMBSync I use to keep music synced from the server to my phone, no streaming services.
I think that covers the main things. Highly recommend CalyxOS, just make sure you don't depend on Google services you'll no longer have (like Drive). Replacing those is doable but there's quite a bit of setup, and possibly some custom "glue" code, to make it all 100% automated/wife friendly.
One other thing - if you have paid apps and they only license through Google Play, you lose them when you no longer have Play services on your phone. This isn't a big deal to me, but may be for you.