I guess I could tell them that they have to have a GMail account, and explain on surname.com how to set up Send As?
Then just host the MX at a host which allows me infinite forwards?
But with spam stuff, that would not be ideal.
I'm also a bit fascinated at the potential that you have 100+ people that you are related to but that you're not close to who would opt in to changing their email address onto one that you have ultimate control over.
I don't want to have ultimate control... I would love to pay this for as long as possible, and let it go.
I ain't young, I got maybe 20 years left. But I just figured that I was not the first person to face this type of issue.
That's been easy for anyone to get if they were willing to pay and spend a few minutes of research. Most people just don't care.
Even if you spent the money on a Gsuite user for every person, you probably wouldn't get more than a tiny handful of users, and most of those would probably stop using it once the novelty wears off.
Are you sure this is even a problem worth solving? What about just inviting those closest to you and asking if they'd want to pay you a few bucks a year for a special email address? Probably it won't be worth the trouble for either of you, realistically.
The receive is the socially powerful part. Telling someone: my email is first@last.com is the general power/benefit. If anyone wants a real email account at the domain, then we can talk more.
Also, be prepared for the tech support questions, the "I never received an email from X that they swear they sent", the "My emails seem to take ages to come through", the "My emails are ending up in the recipients spam folder", etc...