My suggestion you need to be bold of giving the timeline when it started and when it ended, since the celebration is 14th next month, I would suggest the contest will start from February 14th to March 14th, one month is enough.

In the previous contest, you're asking it's need at least 10 members to join for the contest will be valid. I would suggest you should run the contest regardless how many participants joined. Let's say only 9 members join, it's not fun if the contest will not be valid.

Another suggestion you should offer the prize able to convert to Bitcoin, some people who have high privacy don't want to get collectible.