I'm about the shoot a promo on steadicam (AF100) where I'll be moving at a reasonable pace and the kids will be crossing and moving beside me. I'm wondering do I shoot in 25p, 50p or do I shoot interlaced?

i wouldn't shoot interlaced, and with 50p you can even do a decent slow mo, or just a speed ramp ( if you want to)

25p is filmic but i have a lot of stobbing (sorry dunno how to discribe it properly) problems. Its like the frames cant catch up.. Yeah so 50p is nice!

Do you want a slomo effect? Go with 50fps.

For normal filmic look, go with 25fps and 1/50 shutter (180 degrees, in film terms). If you don't like the amount of strobing, then try some "slow shutter" speeds...1/25, etc. But undertand you will be trading strobing for smearing/blur.

I see lots of footage with the shutter (deliberately or accidentally) cranked up to 1/100 or more, and it looks very strobey.