Will they not go in normal bath
Ask the apartments owners mother/grandmother. The Greeks are very accommodating. I’ve bathed, well the wife has, bathed the grandchildren in the shower tray before now. Just block the plug hole up.
Can you not use the sink?
We got a kids inflatable boat for use in the pool, filled it with warm water and Leo who's was 2 1/2 had a boat bath every night...he loved it!
The OP asked in July!
Delete it or it could go on for years!
Will be very smelly kids if not sorted by now 😊