i love musicals, and Lord Andrew Lloyd Webber is the lord of musicals. the music he makes is legendary and the work he put into this one added to his fame.
but enough about him, the movie itself is pretty well made, even when there are a few mistakes here or there. but the big problem is the sexual references. during the number 'Music of the Night', the phantom starts touching Christine in ways that is considered sexual. and during 'Past the Point of no Return', they keep on says phrases like 'bodies entwining' and 'becoming one' (there is a popular rumor going around that during that one scene the actor who played the phantom got visibly aroused, just look for any signs of that towards the crescendo of the song). and there is one make out scene at the end between Christine and the phantom.
the violence in it shouldn't be too much of an issue. but you do see the phantom chasing a man and then strangling him with a noose right before his corpse drops down onto the stage. and there is a sword fighting scene where the phantom gets Raoul in the arm and is able to draw blood, but its just a little bit on his shirt.
the alcohol content in it is very minimal. from just my memory, i only remember the use of alcoholic beverages was at the beginning when a dancer is seen taking just a small sip from a bottle, and during the masquerade scene were the stage hands are celebrating with getting drunk, but theres just a few seconds of that.
so parents, if you don't mind your child seeing anything like this, they may be able to see it alone. but if they are young, you should see it with them for their sake.