An excellent movie that I had know idea what was in it (except for the "I'm Spartacus" line), I first watched "Spartacus" in Latin class as a freshman. It was highly entertaining, and I must say, excellently done. The makers of "Spartacus" carefully censored the sexual situations, which there are maybe two, and nothing is shown that might cause worry. The violence is pretty bloddy for a movie of that time, but wouldn't go past a PG-13 rating nowadays.
I am usually pretty confident, with movies from this era, that there will be very little to concern me by way of sex or violence compared to what would be considered (not by me) acceptable in a movie today. It will probably depend on your child but my seven-year-old and nine-year-old girls are used to being around the boys' (12 and 10) video games. They all thoroughly enjoyed this movie, especially the 12-year-old who has been studying the Romans at school, and the rest of them learnt a lot about the Romans, gladiators and slavery.