I'd echo what was posted about screenings and going to known celebrity places for your daughter. Though in all cases it'll likely be a stare and gawk type deal unless it's some sort of meet and greet.

Out of the studio tours, I like the Warner Bros (due to it's size and scope) and the Sony Pictures one (as it's smaller and more intimate). But as all the shows will be on hiatus, no actors will be around to meet. The upside to that is that since they're not filming, the tours may bring you onto the sets.

I'd also approach this from a different angle. I worked in the industry as a camera assistant in the mid-2000s. My advice here is more for your son than your daughter. I'd suggest having him work on a small film while you're out there if possible. There are always short films, specs, student films being made that your son could work on. Bear in mind, you have to try to pick wisely (if it's too good to be true, then it is) and realize that he likely won't get paid though they'll probably feed him. Also it's unlikely he has enough experience to be a dept lead (like DP or Gaffer) but could very well work as a dept grunt like camera assistant, grip or electric. Making films on your own is one thing, but to work on bigger scale production is whole new experience. One thing to keep in mind, this is only really something to do if your son is mature enough to handle himself on his own. You nor anyone else can hang around set to supervise him. Drop him off and pick him up.

I also would not suggest that your star-struck daughter employ this strategy to meet stars. A set is to work and no quicker way to get thrown off a set than to walk up to talent and ask for a selfie.

The other thing that your son could do that would be less commitment but would be interesting is to volunteer to do a "check-out" with a camera assistant. This is the day or half day that a camera assistant spends at the rental house verifying that everything works the way it should. Many assistants including myself got their start offering to be a helper to a working assistant on a check out day. Once again (and if you haven't noticed a theme here), there is no pay and in this case, likely no food. And most of the experience is just watching and learning. Most of it is grunt work, carrying cases, etc. But if he does it for a big production, it'll be with big boy equipment like an Alexa, pro lens and AKS.