Teach how to use iMessage or whatever your family preferred messaging app…including how to add photos. Teach how to close tabs in Safari (my parents had more than 244 tabs open on their iPad that was slowing down and crashing). If other family is using Facebook or instagram or anything like that set up an account and show how to use the apps.
Make sure when you explain it and show them you give them the phone and make sure they can do what you just showed. (My mom likes to write stuff down while I show her and then I say “no you do it”. Show how to use maps for directions. Add them to Find My Friends to help “keep in touch”.
My mom has an android smartphone and that seems more complicated than iPhone with several messaging apps and browsers.
Buy the 4K TV now. Next year buy a new TV?