I explain it by shopping!
We have a row of ladies shops selling ladies things eg diamonds, cup cakes, handbags, chocolate
And a row of mens shops selling man stuff from man sheds
There can be an assistant of either sex serving you
If you are the shop keeper you must not move out of your shop or you will get burgled!

Top couple go shopping.
They take the car and do a few handbrake turns while they decide which town to shop in
Using left arm Man will buy something for his partner in the Ladies shop and she will get something in the Mans shop for him
Shop keeper holds out their left arm enticing person into their shop in a cunning marketing exercise
After the turn of the purchase they go back into car with right arm to partner and discuss what they bought then off to the next shop in the street.

Next couple get shopping once the high street is clear because you don't want to queue in the shop!

I also adapt depending on audience to Tall People and Small People

At a wedding I will wait for bride and groom to return to top & get them to do a STW down the line on their own. Then all make a tunnel and bride and groom return to top but couples follow down and it sort of regenerates and then finish with just bride and groom running up the tunnel on their own

Mad but it works!