I have done some evening photogaphs in our local school hall and I woud agree with the previous posters that your DA70mm f2.4 will be your main lens and it will do the job.
However you may want to ask the organisers and artists for permission to use flash. You will be get the best shots without flash, but you want the option. A good quality flash (not the pop up) may assist.
In advance, charge fully your battery, empty (or reformat) your card, and, as stated by interested_observe, consider to have a spare (charged) battery and a spare card.
Hope that the comment will help.