You can check the wiki for the home harem beach date: https://wiki.andrealphusgames.com/wiki/Home_Harem#Beach_dates_(seasonal_event)
Regarding your other issues, the stats and story tracker of the girls/harems would be welcome to help you :)
thanks for the guide. as for the stats, they are all at the maximum on all girls, the quest tracker says:<img src="https://img.itch.zone/aW1nLzExNTg3NTQzLnBuZw==/original/uq1E2S.png">
