I have two cats and one of them stinks. We have to spray whereever she has sat with Febreze and then once a month, I wash everything down with a diluted biological washing powder solution. It's the only way to dissolve the enzymes from the pet mank smell.
We also wash the smelly cat once a fortnight - she hates it but I'm not having a stinky house.
I know what you mean about smelly kids though, I've met a few pongers. I found out with one it was because he ate all meals with lashings of tomato sauce and was v keen on egg sarnies (urgh). So he was pretty much constantly chuffing.