My two cents.
My favorite 35mm lens by far is the 85mm 1.8. It's very fast and allows for awesome shallow DOF, which is quite important when shooting kids candids, as you can't always have a perfect background. When working with a single subject, I almost always shoot at f/2 or 2.8. I would recommend getting the fastest lenses you can afford. There's a big difference between 1.8 and 2.8.
I love (LOVE!) my 24mm (wide angle) lens for my Canon. It lends such a unique perspective to wedding and candid work. The last wedding I did was almost entirely reportage, and I used the 24mm extensively. I'd love to get a tilt-shift 35mm lens, but I've got other priorities first.
For the wedding ceremony itself, which was held in a very dimly light, large church, I rented a 70 - 200 f/2.8 with image stabilizer. It was indispensible for the shutter speeds I was getting, which were in the neighborhood of 1/15th at 2.8 with ISO 3200 film! The IS allowed me to handhold, which is critically important to me with my style.
My only MF lens is an 80mm 2.8, although I frequently borrow and need to buy the 150mm 3.5. Fabulously shallow DOF when needed, and much more flattering for portrait work, particularly close up. As an aside, I found the Bronica Zenzannon lens to be every bit the equal of the Zeiss lens I used on the hassey I shot for a few months.
Zooms are great for certain things, but I never use one unless I really, really need it. I find that they're still not as sharp as a fixed lens, and you can get yourself in trouble when handholding them. If, for example, your meter reading calls for f/4 at 1/90th, you can handhold just fine at the 70mm end of the zoom, but once you zoom in, you're suddenly trying to handhold 1/90th at 200mm and you may not even notice. The result: lots and lots of images ruined by camera shake. As the quote goes, the best zoom lens (IMO) is my feet.
If you go with a 50mm for you 35mm camera, it's a great lens, but be careful -- if you try to shoot close-ups with it, you'll get a mild "dog-nose" effect, as there will be some lens distortion. Not generally a very flattering look! You can get away with it with children more often than with adults because they generally have smaller noses and less defined features, but IMO it's better to get a portrait lens if you're going to do portrait work. 85mm is perfect for me, but 105-ish would be awesome, too.
I do use MF for kids candids, but it is significantly more difficult. MF requires me to anticipate, whereas 35mm allows me to react. Both are equally valuable, but look significantly different. These days, I find myself using 35mm more and more due to terrible eyesight and the need for auto focus.