It is shotgun answers to your question, because it really depends on what style of shooting you like to do and why.
For years I carried nothing but a 35mm F/1.4 L and a 24 mm with me everywhere I went. I never felt limited. Later when the IQ became comparable with the EF 24-70mm II I usually just carried it. Many of the venues you mention and shooting inside those venues you will have no tripod. Speed is of the essence as well IS would be extremely helpful. I have shot many interiors in low light with my EF 24-70mm II wide open at f/2.8 and had great results. You can get a used version around $1,200. If weight and mass are an issue, I would probably only carry a 24-70 f/2.8.