You're going to have to trust your parents here. This one's... a little weird. (88 minutes)
Thickly laden innuendo among the ladies of Castle Anthrax, capped off with references to spanking and oral sex. Profanity and toilet humor. Absurdist use of death for the sake of comedy. Graphically fake gushing blood (e.g. the Black Knight scene), but your kids have likely already seen Annoying Orange. I might suggest turning on English subtitles, to help kids parse the dense language and unfamiliar accents. Be sure you’re not turning on the English Subtitles For People Who Don’t Like the Film (at least not on a first viewing).
Then again, African swallows are non-migratory
After a friend’s failed attempt to introduce Holy Grail to his sons (who were too bored to continue just three scenes in), I was hesitant to spring it on my own ten-year-old. But despite forty years and the unfamiliar milieu, it turns out the Pythons do retain their capacity to surprise, startle, and delight future generations of comedy nerds. Kids will be unaccustomed to absurdity on this scale, and may require assistance acclimating. If there are two parents available, maybe have one let the kids in on the secret that the film begins with a completely unrelated short entitled “Dentist on the Job,” while the other parent plays up their confusion (not difficult, as this bit was only added in 2001). Once the unseen projectionist corrects the error and the “real” credits begin, I’d suggest attempting to read along with the fake Swedish subtitles beneath them. Your kids may find this annoying, then confusing, as the møøse references begin to pile on. Before the credits had ended my boy was cackling in uncomprehending disbelief. Everything’s here as you remember it.* The coconuts and swallows, the French taunting, the scientific proof of why a witch weighs the same as a duck. The film might not change your child’s life the way it did many of ours. But hearing my son giggle at Herbert’s father giving instructions to the guards (not to let the prince out of the room until he gets back) was a moment I realized I’d been waiting for, since before he even took his first breath.
*There is one added 24-second bit, in which a scene is interrupted with exhortations from characters from other scenes to “get on with it.”