If the pics were taken the 13th she was probably flying back from Portugal.
On the other topic I don't think the casiraghis are usually accompanied by bodyguards.
The certainly have them when they go to public events, or whenever they are in Monaco or places usually hunted by paparazzi, but it's been obvious more than once that they were unaccompained. I thinking of some pics of Andrea in Rome getting into a fight with a paparazzo and some holidays of him in Ibiza, when she was going out with the actress wanabee Maria Jurado, and the journalist were sorrounding them and asking them questions and he was very annoyed but there weren't any bodyguards around.
So my guess is that they have bodyguards in public places or when they expect public atention, but do not use them in their everyday lifes.
Also the guy in the pics with Charlotte probably is a choffeur/bodyguard, not just a guard, but the guy sent to pick her at the airport