Quick Take / tl;dr
The quick parent's guide: PG. A short list of PG movies that could be used for comparison includes Frozen, Brave, the Despicable Me trilogy, and the How to Train Your Dragon series. If you are uncomfortable letting your kids watch those then you should consider your kids a bit too young for D&D.
The Details
Dungeons and Dragons can cover almost anything that can be imagined. Some sessions focus on wild combat, while others can dig into interpersonal issues, intrigue, and exploration. Adult sessions sometimes delve into subject matter that is very inappropriate for younger participants. Being clear about what can happen and what is allowed becomes critical when your players are not part of your immediate family.
I learned that lesson quickly when I started DMing. Having a list of taboo subjects helps ensure that a session doesn't swerve into territory that makes players uncomfortable, and it can also help put parents' minds at ease.
On the other hand, D&D inherently involves conflict and will have some violence. That violence is abstracted to some extent and couched in fantasy terms. But with careful planning and practice, how it is handled can be compared to the PG rating of movies.
Recently I have learned of a nice technique for further distinguishing subject matter: Lines and Veils. The idea behind that is that for some things there is a line that must not be crossed, but for others, they can be hand-waved in a sort of “fade to black” of pulling a veil over the problematic details.
As an example, I expect that anything involving romance will be a line that won't be crossed for parties with younger kids. But for older teens, not including some romance could make the world unbelievable so anything dealing with romance should be done behind a veil.
Session Zero
In D&D there is often a pre-game session, called Session Zero. This is typically when the players create their characters, get a basic understanding of the campaign world they'll be playing in, and most importantly: come to an agreement on what is acceptable and what is not. This includes player behavior as well as the content.
My courses will always have a session zero where all of this is discussed.
The List
This is the list I have been using for over two years. If you can think of anything that should be added to the list, or if you have suggestions for clarification or anything else, please contact me.
There will be no:
- Sacrifice
- Torture
- Murdering People
- Maiming & Dismemberment
- Evisceration
- Decapitation
- Extensive bodily harm, such as burning alive
- Elements or suggestions of sex
- Implied or outright inebriation or drug use
Player Agency
The content of the game is usually the thing parents are most worried about, but I also want to mention that I try to ensure that the kids are learning the right lessons. One thing I hope most people agree with is that kids need to learn to make good choices.
But some of the magic in D&D shuts players down. While adventures where the players go up against a Medusa, for example, usually have plenty of clues that allow them to make preparatory choices, there are a good number of spells and effects that would appear out of nowhere.
There is a spell Hold Person, which does just that. If it is cast on a person they are frozen - they can't take any actions until the spell is broken. That means they don't get to play and can't make any choices. There are several other spells and effects that do the same. Many of them can just be dropped from the game, while others can be modified so they aren't as bad.
So when I can I avoid anything that violates player agency, and when it cannot be avoided I try to make sure it is something they can prepare for.
My original take on this was free posted on Patreon at What to avoid, part 2 (player agency).