Have you a pair of binoculars you can put some boot polish on the eyepiece. Son comes downstairs with binocs. Says to Dad, "What kind of bird is that I've just seen in the garden over there?" Hands binocs to Dad and..........................................................
Stick a coin to the table with blu tack Shake up a can of pop/beer and pass it to Mr BM to open. Put a toy spider in the bottom of his teacup or in the cereal packet
Move his car around the corner tonight (let little BM in the play and let him in the passenger seat). Tell your son to keep hold of the keys. When Mr BM looks for his car in the morning, little BM calmly hands over the keys and apologises, saying he had to move the car to get into the garage/because a neighbour was blocked in - or whatever would suit your scenario best.