I think they did weigh the pros and cons.
Either stay here, not get papped, but have lots of hideous lies published and get criticised on a daily basis for things that others with the RF are praised for. It would not have been easy for the too disappear as they have to do the charity work all the while being made a laughing stock - tarnishing their reputation so that maybe some charities may not really want to be involved with them.
Or, go away far from the BM, to a place where there are lots of ppl with high profiles and just disappear among them. Sure for the first few months the paps will try for pics, but LA laws mean kids must be blurred. And the novelty of papping them will eventually cool down, I mean how many times did we see Doria walk her dog, even the paps got tired of papping her in the end.
There was that time here in the UK when the story did rounds about them going to a pub. TMZ did their due diligence, like they did with the LA cctv footage. Archie's face is blurred on the pub phone video. What I noticed was that TMZ posted the videos without commentary. No snarky lies made up, what you saw was what you got. I think they prefer pics rather than a smear campaign, after all they don't fall out of clubs off their faces etc.
I also remember the ET reporter saying that the way to get around LA is long established because there have been so many famous ppl there who know how to go about without being seen if they try. He said there are back ways to LAX etc. he figures that is why no one knew H&M were in LA for ages.