This the season to be Jolly! Ho-ho-ho-ho! Yes, I am writing as Doyle, but I am to lazy... as Headmaster this year, I shan't allow any unnecessary festivities and celebrations, nor infantile carols and decoration... that is something you should keep to yourselves....
And, of course, I am joking :-) There's no better time than Christmas time and you will have my full support and participation regarding any kind of activity. Our excellent Charms professor could make the knights sing, and it is something I support and I would also like to state that I agree on making that announcement global. As far as other things are concerned, we should, definitely, organize some form of Christmas festivity inside the castle, being held either on New Year's Eve or a little after Christmas itself. A Ball, a Party anything that would, undoubtedly gather a lot of people in one place. Referring to that, I would also like to invite all ex-graduates, meaning those who have graduated lat term (like Poe, Mari, Sophia, etc.). I think it would be good to see them all back at Hogwarts with their friends and all, and I just wanted to stress that idea out. That would be all for now... and yes, the Gatekeeper should, although I am not certain as to who he is, currently, organize some form of fun activity for the students, especially the younger ones.