When it comes to bike specific lights, mtbr forums take the cake. They have 2 sections, one for DIY lights and then the regular lights.

Now, the only way to blind a driver with a helmet light is A) You have it on your helmet all wrong (you would know this because when looking at the helmet setup, it looks terribly wrong from the get-go) or B) you strain your head enough and aim it at the driver. As for the others in your group ride, when riding you never turn 90 degrees and look them in the face because A) this is dangerous when riding when it is light out and B) just plain stupid.

Our group rides have all riders with pretty much a helmet mounted light, and nobody has been blinded yet. When we stop at a section and chill for a minute or 2, we tend to turn our helmet lights off so we don't blind each other.

I noticed you are riding a trail, and if there are any turns that can be somewhat sharp, a helmet mounted light is really nice to have in addition to a bar mounted light. This way you can look into the turn to see if there are any hazards. I don't care if you put 3000 lumens on your handlebars, it won't have enough spill to cover most turns. With that said, you want the lightest possible light you can afford, so that takes out the Serfas lights and the NiteRider MiNewts, however they have a mini-usb 300 that has an external battery at Performance for like $90 that fits this bill almost perfectly.

The CygoLite would be good for your bars no doubt as I use one on my bars when I ride at night. I like the flood on the bars and a spot on the helmet. If Lezyne had helmet mounts I would probably have a complete Lezyne rig going because I think they have the best bang-for-the-buck lights right now that I have seen in person.