"Kingdom of Heaven", while mildly entertaining as fiction, took huge liberties with the history. Between using real names of people but hugely screwing up their actual roles, and bizarre quirks in the combat sequences (where was that huge flat spot outisde the walls of Jerusalem supposed to be, anyway?), it's certainly not what you would want to use for study material. I mean, the guys who were supposed to be Templars were clearly wearing a French Crusader's Cross, and the actual colors of the Templars were nowhere to be seen... it would be hard to screw up the costumes much worse than that, short of dressing them up like samurai or something. However, it might make for a fun party game - "pick out as many historical errors or logical absurdities as you can in this two-minute clip".
And yeah, if you just want the 5th grade version, lots of pretty pictures in the Osprey books... and occasionally they will point you to some good research, although I haven't seen the ones on the Crusades period, so no promises there. For a little better material, try the bookstores of local colleges - see what their profs are using for university-level courses on the subject. (That will both give you the name of the book and a place to buy it, and you might get lucky and pick up a used copy at substantial discount.) Of course, college-level books are often written by someone trying to say something new and clever, so it's best to try several different ones and/or do some research on the authors, to make sure you're getting the mainstream research instead of somebody's pet hypothesis (i.e. Runciman's work, previously mentioned - usable if you know his bias, confusing if you thought it was the mainstream opinion).
