all those lenses are pretty slow, the 5100 is a decent body but, like luckyse7en mentioned it'll be hard to get sharp shots in that lighting at all, especially with slow lenses. but there are some things you can do that will help
in order to keep noise down, you'll want to shoot at the lowest ISO possible, which also means that shutter speed will need to go up, and/or use larger apatures. and with longer shutter speeds, you'll get much more camera shake, and motion blur...
for the 5100, personally I'd probably try to stay at or under 800ISO if the noise bothers you. the 10-20 will give you less camera shake in the pics, but it's still slow. If you can, try using a tripod and remote release, but slow shutter speeds even with a tripod can have motion blur from the performers playing their instruments. you can go a little higher in ISO and try to remove the noise in post processing too, but I'd rather not have to use noise reduction software if I don't have to.
If you have some money available, you may want to look into getting some faster lenses which will allow you to open the apature larger and let in more light, that will let you get the same amount of exposure with faster shutter speeds, and lower ISO.
depending on what focal lengths you like to shoot at, some "less-expensive" options for faster glass would be: nikon 50mm f1.8D (or G), 35mm f1.8G, or the 85mm f1.8...or you can look at various other manufacturers like sigma I think makes a 24mm 1.8 and 28 1.8 though I don't know what those cost....you want to get the smallest f stop value (small f-stop numbers mean larger apatures, just FYI incase you were unaware, since you said you were just starting in photography)...I've shot some small performances in spaces similar to what your pictures show, and I found I liked wide angle lenses more than longer ones. I'd say look at the 35mm 1.8, or possibly the wider sigmas or something...
there are also camera bodies that can handle higher ISO while still producing low noise, however depending on your budget, those can cost a good amount. and the 5100 is a fine body. its best to hone your skills and upgrade down the line if thats something you require IMO....