and a prime lens like the 50mm f/1.8 or should I skip the kit lens and just get the 50mm and a zoom lens like the 55-200. My main uses will be takings photos of my 2 and 4 year old in our dimly lit house as well as taking photos of them outside while they are playing. My 4 year old is playing soccer now so I would like a zoom lens to take some photos of him. This is my first DSLR so I'm pretty ignorant on this topic. Any help at all would be greatly appreciated.
I suppose the best answer really depends on what your available budget is, on the whole. The 18-140mm is going to be pretty decent for daylight outdoor or very well-lit indoor situations. It also has a decent range for most close-to-medium distance situations. As soon as the lights/sun goes down, you're going to find yourself cranking up the ISO to capture images, especially when you're talking about trying to capture images of young children. The apertures on the 18-140mm (as well as the 55-200mm) aren't that big, so they don't let in a lot of light. To properly capture motion in dimmer lighting, you'll have to set a higher shutter speed along with a higher ISO sensitivity.
The 50mm f/1.8G will be a decent performer in lower light situations, and, with a little skill, you can capture plenty of action with it. The only downside is, as obviated by it's single focal length, it's not an ideal lens for every situation, such as close quarters or photos where you want to include more of the landscape, which is where a wider angle lens would come in handy.
What's also worth mentioning is the 55-200mm isn't exactly known for it's sharpness. If I were buying a 24MP camera that had no optical low-pass filter, I'd want a set of lenses that can possibly take the best advantage of that feature. I don't think the 55-200mm would ever come into consideration. Then again, I don't plan on making prints to fill the side of a bus, and I'm betting you won't be, either. (Just for reference, an 8" x 10" print at 300dpi is a 8MP image.) But, still, a sharper lens would at least allow for cropping an image & retaining quality, if you need it.
If I were in your position, and I had a reasonable amount of cash available, I'd get the following lenses:
Nikon 50mm f/1.8G for low-light indoor
Sigma 17-70mm f/2.8-4 or 17-50mm f/2.8 for good-to-moderately-dim indoor/outdoor
Tamron 70-300mm f/4-5.6 for outdoor sports
True, if I had unlimited funds, I'd get a bunch of f/2.8 zooms, the best prime lenses ever, and a D4S to match, but I'm assuming you're going with this camera for a number of reasons, and I figure these lenses will be a good match. None of them are awfully expensive, they're all better than the base products available (some by a decent margin), they can often be had on sale or used (I only have one lens I've ever purchased new, the rest has come used via Amazon, B&H, or Adorama), and they'll produce pleasing images.
I hope this has been helpful.