The dad likes being treated like a kid but who doesn't.
mom took dad on a ride -> sex, stayed in the park for 9 month, 4 child was born.
A dad a mum and three kids go on a family vacation to a theme park.
Next the mum takes the dad on the dragon ride.
And the son takes the mum on the water slide.
Lastly the dad takes the mum and all 4 kids back home.
Take every first letter of the sentences easy
Mom is actually his daughter
Mum and son are the names of 2 kids, dad is with 5 kids after all