As much as the family may not like it, they may be better off moving into a motel until this is resolved. Pay a few people to stay at the house for a week, set traps, lie in wait during the night. Worse comes to worst, they may have to move. I’ve heard of snakes taking over a house the same way.
They may live deep into the earth and have lived there for decades. A monitor lizard that size could bite the children severely.
Any Komodo Dragon in Florida? Septicemia from a bite.