The idea isn´t bad at all. People like to a challenge -> farming all Cards / Upgrades. And if you maybe give the chance to spend some money for some extra Packs, you probably make some ppl who like getting stuff faster than others happy. I personally don´t care about charity, but i like to spend money on things i like. For example i really liked the promo swamp drake, so i bought it for about 80€, stupid but worth.. i guess. And if you take some of the money and distribute it bettween the helpers of the project no one would mind and it could be a motivation to keep things going.