It was almost impossible to gather everyone--Alix and MF were the most devoted. Even the Crown Prince, who lived in Denmark, was sometimes not there due to the treatment of Louise.
Ernst Cumberland hardly ever went, Bertie probably even less. AIII was the in-law there the most it seems. CPss Louise was uncomfortable and seemed to trail off going.
George and Eddy were often at sea, GV especially once Eddy returned to go to university. GD George's illnesses would catch up with him.
As the generations aged, two of the most prominent descendents, NII and GV, didn't seem to go much--NII went to some occasions, like Queen Louise's funeral, but without Alix. May was there once or twice but GV wasn't ever as dedicated to going, probably because he hadn't gone much as a boy and young man. Queen Sophie of Greece went, but I don't think I've ever seen pictures of those gatherings. Plus, the former Crown Princess Louise, once she became Queen, didn't have much desire to gather everyone together. Sad, really.