Mom and son's friend

[artlover321]

Looking for a story that is probably 10 years old or older. In it a married mom is asked to keep an eye on her friend's son (her son is friends with the kid too) while the kid's mom is away. The mom's husband and son are also away at a camping trip.

Ultimately the mom ends up seducing the son's friend.

I think it was part of a series and in one of the later stories the two moms end up fucking their sons...