How "kid" friendly is Star Wars VII The Force Awakens?

The BBFC rating page has a summary of what justifies their 12A rating, which may answer your question:

STAR WARS: THE FORCE AWAKENS is a sci-fi action adventure in which a young woman becomes embroiled in a galactic conflict.

VIOLENCE There are frequent scenes of moderate violence, including use of blasters and lightsabers, and dogfights between spaceships. Sight of blood and injury detail is limited and brief.

THREAT Occasional scenes of moderate threat include characters being interrogated using 'the Force', which it is implied causes them pain, and characters being held at lightsaber-point.

There is infrequent use of very mild bad language ('hell', 'damn').

Unfortunately the only thing I can find for the corresponding American institutions is "Rated PG-13 for sci-fi action violence", which doesn't help much.

An unofficial site that often has more detailed ratings/summaries than the official ones is commonsensemedia.org, which says in the main summary:

Directed by J.J. Abrams, the sequel takes place approximately 30 years after the events of The Return of the Jedi, and although there's tons of sci-fi action -- space battles, crashes, explosions, lightsaber duels, and more -- there's less violence overall than viewers saw in Episode III: Revenge of the Sith. Villains do order the mass murder of countless civilians, prisoners are coerced physically and with the Force, and duels lead to injuries and death, but none of it is bloody or gory. With little language ("dammit" and "hell" are as strong as it gets) or sex, this is the kind of epic adventure that will undoubtedly appeal to Star Wars fans of all ages. But while younger kids may be familiar with the franchise and its many spin-offs (like the animated Clone Wars), they might not be ready for some of The Force Awakens' more violent or emotional scenes. (Spoiler alert: One death will hit very hard.)

And in the tooltip of the "Violence" sub-rating:

Lots of sci-fci action violence on both the largest possible scale (planets obliterated) and much smaller (one-on-one lightsaber duels and firefights/shoot-outs), but hardly any blood/gore (with the exception of bloody fingerprints on a white stormtrooper helmet). There's a weapon that can destroy entire systems, and there are explosive battle sequences in which people die and ships burst into flames. Kylo Ren tortures people, both physically and with the Force. Quick glimpses of dead soldiers and civilians lying around. Laser guns of all shapes and sizes (handheld, ship mounted, etc.); bombs. Chases, crashes, and frequent peril. Large, monstrous creatures rampage through a ship; other creatures look scary/threatening, and the leader of the First Order is creepy. A man orders an entire village of civilians/witnesses slaughtered and cuts down an unarmed man. A young man has debilitating anger issues. Spoiler alert: Supporting characters are injured, one is presumed dead, and there's one very upsetting death.

Having seen the film myself, I can attest these summaries are completely accurate, although the mention of "torture" in that last quote may sound worse than it actually is; it's more like "interrogation using the Force" as the BBFC summary says.

Whether this means 13, 10, 9, etc is the ideal cutoff is something only you can decide, but that ought to be enough detail for you to choose.