Giardia?!

Yes it can be recurring and yes they can treat it. Its not fun but really, really common in the area I live. Its also known as beaver fever because it can come from stagnant beaver pond water (in our area anyway).
Do the stool samples and find out for sure, but if it is, its not the end of the world, just not pleasant.

When we brought our dog home from the pound we found out that she had Giardia. Luckily noone in our family got it but we made sure to pick up her poop and then we would bleach the area that she did her buisness. Mixing a little bleach with water and dumping the mixture where she had went. Plus we were told to keep our dog kenneled and away from everyone til she was in the clear. we have had our dog since July and once she was treated we have not had it come back.

get some flagyl(rx) for the dog and the kids - after it's treated, it maybe recur, but it's not usually anything severe. people get it VERY frequently when vacationing out of the country - it's usually just a minor illness, almost like a longer lasting but mild stomach virus.

I wouldn't freak out too much. If your son has it they will provide a dewormer so to speak and completely get rid of it. It won't be recurring if you make sure your dog has completely gotten rid of it. Just make sure to pick up all your dogs poop in the yard so there is no re infection and wash wash wash your hands. Even when you change his diaper too. Keep your sons hands clean too. Hope this helps.