sevo
Fokutorendaburando
Bosco -
If you'll be shooting a lot of skating/BMX I would recommend you consider an AF body. I used to shoot pool/ramp skating and velodrome bike racing, and AF can make a big difference in the number of "keeper" shots you get.
If you pick a camera with a focus trap function, yes. I've never had (or have seen) a camera able to AF track skaters at the distances common for the usual (rather close-up) shots. The F100 may be the lowest end Nikon that can trap focus - perhaps the only outside the pro series (F5/6, plus F4 with accessory computer back).
But focus trap is essentially all manual except for relieving you of having to release the camera exactly when the skater is at the pre-determined spot - once you have figured out the pre-delays of your brain and camera, you can be just as successful releasing by hand, so any reasonably fast and snappy all-manual camera will do as well.