Still Not My Fault by Misty Malone

Denny and Randi, the characters you met in Not My Fault, adopt his niece and nephew when they become orphans less than a year after the couple is married. Christmas is approaching and Randi wants their first holiday season as a family to be special. They do all the traditional things both of them did with their families, plus everything other people told her their family generally does.

Mixed in among all the special holiday things they do, Denny, who is a detective, is working on a case which is sending people to the emergency room with stomach problems. It's not a disease and is not contagious but needs to be solved, with the holidays coming up.

Can he solve it before someone gets seriously sick before the holidays? And can the family get all the things finished they plan on doing before Christmas morning? The result of their efforts is one happy, but worn out family.