I have to disagree with mattdm on his first point. Always use the centre focus point and recompose after focus-lock has been achieved. I can't imagine a situation where you'd want to use any other focus point. If you have lots of time, using the centre focus point and recomposing will give you more freedom in composure (as you won't be locked in to having the point you want to focus on be at one of the 9 default focus points. If you don't have a lot of time, deciding on and then selecting the focus point and then shooting takes up piles of time - far more than even focusing, locking and recomposing would. Traditionally with action photography you want your subject centred anyways (as it's all you have time to do), so the centre focus point will most likely be the one you select anyways.
As for automatic modes, I like aperture priority myself. Shutter speed doesn't particularly matter in most situations as long as it's fast enough to handhold while having a photo that is technically correctly exposed (in that enough light got to the sensor and it's sharp) but has an aperture 2 stops too fast will more likely than not result in an bokeh-fest completely lacking in detail in any plane outside that of the focus point. However, this mode does require you have some basic knowledge of photographic theory, which leads me to...
Books! You are going to buy, borrow, rent or steal and read the following books before your trip:
Understanding Exposure: A wonderful book by Bryan Peterson. It'll give you piles of knowledge in regards to the effects of the shutter speed, aperture and ISO you select and some very good rules of thumb in regards to each.
Magic Lantern Guide to the K10D: Really a simplified elaboration on the official manual of the K10D, it gives you some more info on what your camera can really do in less technical terms than your manual uses. By the sounds of things this book will really help you out.
Lastly, your manual. Cover to cover. Probably twice. To use your camera to its fullest you need to know exactly what button does what when used alone and when it's used in collaboration with any other button on your camera. Off the top of your head you should be able to tell someone how to turn on bracketed exposure, what pressing the OK button in tandem with turning the back thumbwheel (changes ISO), the difference between AF-S and AF-C focus modes and how to change your flash exposure compensation without a single 'Umm...'.
As for low light photography, there are two ways to do it right: A tripod or a fast lense coupled with high ISO. The latter is only one way to do fast-action low light photography. Luckily for you, your 50mm is damn fast, so I will offer some suggestions regarding its use:
Be extremely careful with focusing when it's wide open. At f/1.4 your plane of sharpest focus will extend a full 1.4cm from the point you focus on back, so if you do want to use this aperture (which is wonderful for portraits [b]if you are careful to focus on the eyes of your subject[/u]) be extra-triple careful that your focus is absolutely perfect. If it is not, assuming no undue luck or divine intervention, your photos will be unusable. The lense is at its sharpest from about f5.6-8 and deteriorates as you go in either direction from that range, so when you're in sunshine or are taking a long exposure on a tripod anyways and don't need any special bokeh that's the aperture range you should be shooting for. You perhaps may want to open it up a bit more than that even if you're in sunshine but are doing portraits, as that particular lense is clinically sharp at its best and a slight softening can actually be quite good at hiding blemishes of the skin.
I also advise you not to be afraid of cranking the ISO all the way up to 1600 if need be. Your image quality will of course suffer slightly (aside: the K10D with latest firmware is quite good at high ISO - rather film like grain rather than ugly chroma noise) but a slightly grainy image is far better than a shaky mess caused by too-long-to-handhold-you-fool shutter speeds.
Well that's all I can think of at this time. Please ask more questions (either new ones or asking to clarify what exactly I meant by the mess typed above) if you have them and most importantly have a great trip!