L.S.
Just ask them how you should proceed. your grandson is also just showing off. If you can take him off their hand for any amount of time, then I doubt they will not want you there. My nephews always act when I am visiting. It is for attention. Also, I am not as good at being strict with them when the parents are around, but when I am babysitting, I don't put up with any nonscence. Just ask your son what you should do.