This isn't a follow up from Adventures with Mum's, but it does feature the same characters, like an alternate universe type thing. Gemma gets the chance to stay in a cottage on the coast for work, and takes Mike and his friend Scott as it coincides with Mike's birthday. The boys procure some aphrodisiac pills hoping to meet some girls, but unexpected things happen.
A family discovers its secret tradition when it is forced to resume them, and horror turns slowly to acceptance and enthusiastic embrace. Based very lightly on the works of H.P. Lovecraft, but without tentacles. Written from the father's point of view. A little bit slow to start if you are reading it just for the sex.