How do I behave in the funeral of my boyfriend's son?

I've been away for a while and I am happy you guys are still here. My son's boyfriend died yesterday as a result of a motorcycle accident that occurred two months ago. We are all so devastated, but I can't compare with my boyfriend's pain. I am concerned about the wake, the funeral and other activities concerning this tragic moment. My boyfriend wants me by his side and I am fine with that, I know he feels better when I am with him, but I feel the right thing is for the parents to be together. I want to be there, and I will be there when my boyfriend needs me but I want to be more as a guess, more on the side so that mom doesn't feel uncomfortable. What to do? What do I tell my boyfriend?