For non-technical family & friends? Forget about it.
2. Set up auto forwarding
3. Done
I have seen people bitten pretty badly by "if I set up X in Gmail, they'll faithfully keep doing it..." assumptions.
4. Gradually move things over to the new address as you notice things which still use the old one, possibly over the course of years.
Eventually you will run out of reasons to keep your gmail account and you can just close it. I migrated from gmail using this approach and it was not difficult in the least.
At $Work, we received a domain registrar password reset e-mail today - for a former client who I don't think we've talked to in 15+ years. Banks, registrars, etc. seem to store stuff like e-mail addresses in more different fields, in more different databases, than any 3+ of their customer service rep's can find & fix right.