I'm wondering why you decided to avoid regestration for you users? Yiu know, we all get used to to do this and I have some starnge feelings abot that like it's not safe or something..maybe I' paranoic a bit 
I think that it's even no need at such services ..Through the website I can see that they have strong sponsors and a couple of my acquintances are using it. So, I think you don't need to worry)
I consider that there are no reasons to worry cause the platform is powered by such reliable services as Changelly, ShapeShift, Evercoin, Bittrex, Poloniex and others with no additional charges.