Thank you all for the replies.
What I mean by clearer is the blur. Right now when I try to take pictures of the little monkey I'll get 1 out of every 6-7 to come out crisp with the others just fuzzy/blurry.
Yes I do need to learn a lot more about the setup. The search for a new lens was from other friends who have the same basic Costco box I do and say a "better" lens helped make their shots cleaner (no blur).
I'd say that its a 70/30 split of my shots being outdoors vs indoors. I do have a flash which made a big improvement in the indoor stills, but sometimes I still miss then running around shots. What I am hoping to find is if I get a <insert type> lens I will be able to take more shots of my toddler as he's running around finding trouble but still have good portability (so yes maybe the 135mm is too big).
edit: I do not have a UV filter on
Ok I somewhat suspected this was the case. I don't think a new lens is going to help your problem. If 1 out of 6/7 shots come out crisp it is not the lens that is the problem, rather technique. The good news is you don't have to spend any money to correct your problem! The bad? news is you can't just buy a new lens and correct the blur you are experiencing in your photos.
What you are experiencing is called motion blur. You only need to understand the basics of your camera and you will be able to greatly improve that hit rate. Basically, in order to stop motion you need to have a shutter speed fast enough to 'freeze' the action. You can experiment with faster shutter speeds until you find the speed needed to freeze your children running around. I would start at somewhere around 1/360th of a second however they may require higher depending on how fast they move.
When your friends said a better lens made their shots cleaner, they were probably referring to noise, not motion blur. And a new lens with a higher maximum aperture can help you reduce your shutter speed and ISO and in turn reduce your noise.
The basics of photography revolve around three things. Aperture, Shutter Speed and ISO.
Aperture is basically how wide the lens opens when you take a photo. The wider or "faster" the aperture, the more light is let in for a given shutter speed. Shutter speed is how long the shutter remains open, obviously the longer the shutter is open the more light is allowed to enter onto the sensor. However if it is open for too long, your subjects will blur as you are experiencing. ISO is how sensitive your sensor is to light. You can think of it as digital amplification of light.
These three things form a triangle, when you decrease one, you must increase another to let an equal amount of light hit your sensor. For example, let's say take a photo of your child at aperture f/5.6, shutter speed 1/320 and ISO 800 for correct exposure, however you are getting blur. You need to increase shutter speed to freeze the motion- to do this let's say you decide to double the shutter speed to 1/640th second. This will freeze the motion, but it will let half the amount of light in, so in order to maintain correct exposure you need to double the light sensitivity with either Aperture or ISO. Your maximum aperture is already f/5.6 so you can't go any higher. Your last remaining option is to increase ISO, doubling it to 2000.
The downside is high ISO creates noise in your images. A way to obtain better image quality is to use a wider aperture instead of a higher ISO. That is why a new lens with a higher maximum aperture can help you get clearer images. You will still need 1/640 or whatever the higher shutter speed may be, but you may be able to use f/4 or f/2.8 aperture and double or quadruple your light sensitivity with that aperture instead of using ISO and dealing with the added noise.
I hope I made some sense. You may not grasp it all straight away however I think I have covered the basic three principles of photography to get you started.
To put it very simply, you need to use a higher shutter speed to fix the problem you are having with blur. You may need to increase your aperture or ISO in order to maintain correct exposure. Or learn how to use Tv (Shutter priority) and let the camera do it for you. If you use Tv mode you are able to set the shutter speed high enough to freeze the motion, and let the camera chose the other settings for you. This may very well be the answer you were looking for.
Let us know if that fixes the problem!