Hi powersnake! Gosh we just love it when contest holders ask for our (expert) advice!
Looking at your entries so far, there are definitely a lot of heavy effects going on there. It's absolutely important for your logo to look good in black and white, so one thing you could do is ask designers who come up with something that you generally like -- but that is maybe quite flashy -- is to ask them to upload another version in black and white only. Or update the brief to ask designers to submit both black and white AND color versions.
As for fonts and colors, I think it's really up to you to decide if those are right for you. Of course, you want your logo to be instantly readable, and in logo design, color can be key. Colors convey emotions (red is aggressive, blue can have energy or be calming depending on the hue, etc.). You could look up the psychology of color on the web to learn more about the emotions that colors can elicit and then decide if you think you've chosen the right ones for your company.
I hope this helps!