The son is 8 years old. (I add this fact, b/c there may be some leniencies to the halacha as he is below Bar Mitzvah.)
Dad wants to begin Shabbat "early" before the "regular" candle lighting time (18 m before sundown). Dad wants the son to come to shul with him. (There is no "community time application" as there are numerous shuls each having different times.)
Mom needs a bit more time to cook the chicken and she wants the son to help her. Without his help, no chicken and mom says, "Shabbat will be ruined!" (OK, she's a nervous mom, but I think she means it, this time!) She needs to start Shabbat later.
For purposes of honoring parents (Kibud Av Va'em), whom does the son have to listen to? If there is a problem of desecrating Shabbat if he listens to mom (as he wants to start later), please indicate why. (In this case, it becomes obvious he has to follow dad who is observing halacha.)
Note: Please don't answer, "Go with dad to shul to ask the Rav what to do." The Rav is in the Catskills for the summer telling others what to do :-)