Best free way I know would be to move everyone to their own Gmail account, forward your mail via something like Cloudflare's new free email routing.
To migrate your emails across you could use the POP email feature in Gmail (set up an app user on your Gsuite first for the POP authentication and make sure you don't tick "keep emails on server" as this seems to prevent it from working).
To migrate your emails across you could use the POP email feature in Gmail (set up an app user on your Gsuite first for the POP authentication and make sure you don't tick "keep emails on server" as this seems to prevent it from working).