The trickle charger will maintain 12V battery but it will not affect the high voltage hybrid battery pack. It's possible the high voltage pack could go flat over three months of inactivity, but I think in most cases it should be fine given that the winter is almost over. I would recommend that you follow the self-isolation advice and address any potential vehicle problems in 12-weeks. A worst case scenario would be the car needing a reset and recharge by a Toyota hybrid specialist (from the dealer). But this would be a small inconvenience compared to the possible health impacts for yourself and your wife if you break the Government advised 12-week self-isolation.