Need advice about what to say to my son’s dad

My 9 year old son stayed the night with his dad Sunday night, and I was supposed to pick him up Monday morning and take him to school. I got a call Monday morning that my son had been up all night coughing and wheezing and did a few breathing treatments (asthma), and that he was too sick and exhausted to go to school. I said ok since that day in school was field day where they spend the entire day outside playing sports. Son’s dad asked if he could stay again that night and if I could pick him up Tuesday morning. I said yes, since my son hadn’t seen his dad in about a month. But, I needed to come drop off clothes for the next day. I get to son’s dad’s house and son comes out to say hi, but won’t look at me, and he’s doing this weird cough. I had my step daughter in the car, and when we drove away she said “it sounds like he was fake coughing” (she is 8). The next morning he is fine, I take both kids to school. When we get home, I ask my son Point blank “were you really sick yesterday?” His face instantly fell and he told me that his dad told home to lie and say he was sick so they could stay home and play video games all day. Needless to say, I’m pissed. His dad is like a big kid who will never grow up, and tries to act like a friend more than a parent. My husband says let it slide, especially since he only missed field day and not a day of actual learning. But I want to say something, at least letting him know that I am aware that he encouraged our son to lie. Any advice on what to say is appreciated. Thank you. via /r/Parenting https://ift.tt/2IDsD5b