I got my RAI today and started isolation. It's not so bad...you get to just relax. My husband is in the house and there's no problem per the radiation doctor. For three days you can't spend time in the same room as others, can't touch anyone or anything others will come in contact with. I covered my tv remotes with saran wrap, wear gloves on the computer and when I'm in the kitchen. I have been told to flush three times, let the water run awhile after washing my hands, clean my sheets daily, and take 3 showers a day. I was the shower and let the water run after each shower. From everything I've been told, it's really a precaution only. If it was that dangerous you be staying in the hospital for 3-4 days. Also, drink alot and constantly eat lemon drops to keep your salivary glands working.
I have two pets. They don't understand and want to come to me, but we put up a gate to keep them out and make sure they don't have contact with me. That will probably be the case with your 6 yr old. You will have to ask your doctor though. To error on the side of caution, they may ask your 6 yr old to sleep out of the house for the first 2-3 days.
Good luck