The students are the ones at the back in the elf suits traditional folk costume. I don't think it's a competition but a tradition that they bring some trees for the RF to chose from.
It's not often that Silvia has her grandchildren together but it seems that everyone is in Stockholm for Christmas.
Princess Madeleine's three - the girls in the patterned skirts/lilac cardis and the taller boy in all blue
Prince CP's three boys - in the blue and red trimmed jackets
CPV - Princess Estelle in the grey dress and Prince Oscar in the grey jacket
Princess Madeleine and Chris O'Neill are supposed to be moving back to Sweden having left royal life and lived in Florida for many years. It was announced 9 months ago that they would move back in August - but it's all been a bit quiet since then.