Its all in the skill of the photographer. You're good to go with what you have. The only thing I would suggest is a wider angle high speed prime to be able to capture some close ups, but you should be able to get them from your 18-135 lens if you shoot at higher ISO.
You can shoot up to ISO 3200 without flash & still get some good jpegs from the camera. Use ISO 6400 only if you can't use flash in a tight pinch. You can get much better results after processing higher ISO RAW files. Set your camera to shoot in jpeg & RAW.
I do a lot of low light photography with my K-50 & get some extremely good results within ISO 800 to 3200. Knowing how to post process the DNG file is the key, though. The noise grain from the DNG file is quite pleasant looking up to ISO 3200. The image quality & noise grain starts dropping off at ISO 6400, but I can still get a very good looking looking 8x10 print out of a processed DNG file. I think I would be able to get a decent looking 11x14 print quite easily.
So if you're confident enough in your skills, you'll be good to go!