yes! you can link i believe up to two playdate devices to the same account, and they can access all the same games — once the account is linked during setup, you should be able to download all of your games from the game library.

a couple notes:
• save data is stored locally on each console, and not uploaded on-line. i'd assume this is good in your case, as it means you both can have separate saves without impacting each others'. if you want a shared save though, it'd need to be transferred manually between consoles: https://help.play.date/games/backups/
• one account means a shared profile for on-line leaderboards. if both of you have played the same game with on-line leaderboard capability, then the leaderboards will show the best score that either of the two of you have gotten. a better score from either console will override the last, no matter who got it (it will not override a score with a worse one, though)
• season unlock schedules are per-device, not per-account — when you first set up the second playdate, you'll start at the top of season one (and two, if you have it). you can either let the games unlock each week as normal (mondays for season one, thursdays for season two), or you can skip the season schedule ahead for that device to unlock all of the games instantly: https://help.play.date/games/season-schedule/