The contest should be simply following the social media (SM) account. That way you get far more entries and an audience who will continuously get Hive in their SM feed.
The thing about advertising, when it comes to the subliminal effects that make it worthwhile, it only works if there is so much of it that the audience is likely to come across it at least 3 times. One banner, seen once and never again is completely ineffective even if placed in the best location. Switching the focus to increasing the number of people following the SM accounts - even if they don't think they're interested in what they're selling - is a strategy that leads to more people seeing it more often. And there's no challenge or cost to following the Account, besides their attention - what we want.