7th Heaven is one of those tricky shows you want to like, but can't wholly endorse. Everyone will have his or her own reasons for this; here are a few of mine.
The Camden family is a close-knit, warm clan. Parents Eric and Annie want their kids to grow up to be good, well-adjusted people. For the most part, they succeed. All seven kids have human foibles, but are mostly sympathetic and relatable. (Favorite and disliked characters vary according to viewer).
Especially in the early seasons, 7th Heaven deals well with universal issues such as friendship, love, death, the consequences of negative choices, and more. Many episodes are specifically issue-driven and include characters such as abused spouses, teen gang members, Holocaust survivors, unwed parents, drug users, and more. The episodes center on how the Camdens help each person in their lives negotiate problems.
The show gets sticky when it comes to the Camden family's own problems. For example, oldest daughter Mary gets thrown out of the house in Season 5 for drinking, bouncing from job to job, refusing to attend college, and behaving selfishly toward her family. Whether Mary's punishment is deserved is arguable, but the family's blindness toward the problem leading up to it is disturbing. Later on in the series, Simon gives away his virginity and has a string of questionable girlfriends. Lucy and Annie become whiny and melodramatic, a turn-off to many viewers. Eric, a minister, writes a racy book and seems to lose or ignore his former moral compass.
In general, whether your family settles in with the Camdens is an individual decision. What you like or don't like will influence whether you keep watching. The only solid recommendation I can make here is, because some issues discussed are serious and potentially graphic, wait until the kids are about eight before letting them watch.