Bruce, first of all, is very generous of you to be a recent member and start with such a massive Giveaway!! 
I am running a giveaway currently and have defined my rules. I will not write the whole text here, so I leave the link for my “rules” here: A GIVEAWAY that may take a while ;) - *WINNER ANNOUNCED* [27th April 2019]
I guess you can define some things if you want (some were mentioned above)
- starting date and end date for the GAW
- number of posts for the members to participate (or not)
- registry date that can be elegible (when the members made they register on BLF)
- special rules (some where mentioned above: making funny posts to say “I’m In”; the members that win your lights have to make a GAW too; members have to make a review of the light; ….and much more)
- shipping costs (if applicable)
These are some things, take it as suggestions 
I do hope to see your own made flashlights being discussed soon here in the forum!!! 