Dear god, one minute the McCann's are behaving weird and not caring about Madeleine because they are playing with their twins, next they are not caring about the twins because they are flying off to put posters up in countries where they thought Madeleine had been taken to, to help find her.
It seems whatever they do is wrong there will always be something to beat them up about.
They are not being strange and uncaring playing with their twins, they probably felt guilty they weren't getting their attention and wanted to spend time with them to make up for all the time they hadn't been there for them. Who wants small children seeing their parents crying and behaving how the McCann's were when Madeleine disappeared? THAT would have been upsetting for them. They kept their routine up so that they could carry on with their holiday and enjoy themselves as small children should. They told them that Madeleine was missing when they asked where she was and that people were looking for her, which is all they would be able to understand, in the meantime they let them know that they were there for them.