your method is like spamer, im not agree with your method, better you give everyone some bits with xapo invited method, so everyone will register and receive some money,,
or yu can send everyone coinbase referal code, then send him some bits, so everyone will get money and if your referal buying bitcoin yu can get some bits too
I don't think dust amount of btc will get ppl interested at it! Probably 0.001BTC worth around 40 cents. You could spread the ppl around you! But it will be costly when doing this to thousands of ppl.