Indoors the 55-300 might be a little long, so of the two lenses you'd probably be better off with the 18-55. I'd push the iso to 1600 and use the flash dialed down a bit as Clicker suggested.
If you're looking for fast prime, but want something a little wider than a 50mm, the Sigma 28/1.8 II might be a good choice if you can find one. I recently picked one up and so far it seems like a good low-light indoor lens. They don't come up often, but if you keep your eye out you might be able to pick one up for around $200. If you were willing to spend about twice as much, a used FA35/2 would be an excellent choice as well.
If you'd rather go the zoom route, I personally like the Kx + Tamron 28-75/2.8 combo. I usually use it wide open and set the iso to 1600 or 3200. Below are a couple shots I have posted on the forum already, but they are decent example of the above combo:
Kx + 28-75 @ 63mm, f/2.8, 1/60s, iso 1600
Kx+ 28-75 @ 75mm, f/2.8, 1/30s, iso 3200