Ugh, We had this problem about 8 years ago...and it's still fresh in my mind.
The itching isn't the worst of it. Having to tear up all the carpet in the house, rent 3 deep-freezes for all the stuff you cant boil for a LONG period...having the grill going with the stove and having to buy lobster/crab pots in order to boil them in the first place, having to (airtight) seal furniture in plastic bags (and then not use them, for fear of ripping the plastic), bleaching everything in sudndry, and having to throw out sooooo many things. That's the worst of it. Hundreds of hours worth of work.
FORTUNATELY, it's one of those things that certain jobs will use L&I for, others will use sick leave, etc. We didn't own our own house at the time, but I would be willing to suspect that Homeowners Insurance might even cover some of the cost.
Gawd. What a PIA.
The thing is...if you dose them now...it doesn't prevent it, UNLESS they already have it. We had to get dosed multiple times (and switched to flea shampoo :P), and finally ended up doing that gawd-awful freeze/boil/suffocate/remove/sterilize procedure. Like you, it kept being passed from extended family & friends...and after a couple months of it...we all sighed & gutted our houses. Signs DO take awhile unless someone is very allergic to the bugs...and during that time...your whole house is being infested.
Ugh. There's a reason why scabies is known as the 7 year itch. Unless you get lucky with a reeeeeeeaaally mild infestation, you have to upturn your life to get rid of them (as does everyone else, or you might as well not do it at all. Blighted things. Give me lice ANY day of the week.
What I would personally do, having been that road before, is wait. If any signs develop, the do the total immersion & overhaul all at once.
However, if you watch other people's children, you would ethically have to either a) stop during the window, or b) dose and overhaul.
My sincere condolences.