I have a couple of questions that you will need to answer before you can plan a movie tour.
Are you looking for actual, serious studio tours, like Warner Bros or Paramount, or are you looking for local places known to be used as sets? (I'm assuming studios.)
How old are your children? Several studios have minimum age restrictions on their tour guests. WB is 8 or 10. Not sure about Paramount. These tours are usually 1-2 hours.
If you want one that all/most of you can go on (small children might be scared), Universal Studios Hollywood Theme Park has an "Interactive" tour of the actual Universal Studios backlot. The hitch is that you are taken into several special effects areas, as part of the tram tour, that may induce fear in little ones - their motto has been "put's you in the middle of the movies". Theme park admission is required.
If you want to see the local area of Hollywood, then a Starline Tour would be the thing. Small children would be bored, but on the van drives around the area, guides point out several places used in the movies. These leave from Hollywood and Highland and take 3 hours.
You should allow about 50-90 minutes to get there (depending on time of day).