I have a knock off that is extremely similar and it's pretty "ok".
You probably want a diffuser if you are running that for a bar light, but maybe the kids don't care? This light will be too much of a spot (but perfect for a helmet light). Here's the diffuser I use that fits that light...
The warmer the better.
I noticed that my cheepo chinese xm-l was actually more purple than my other lights. Not too much of a problem, but I'd like more towards neutral or warm.
I run with both single and dual p7's like this and the second one does make a difference, although I can blaze down pretty technical downhill trails with just one.
Love the battery pack. I may have to do something like this.