In theory (at least in FR land) this sounds like a great deal - not only make money from ads on your website, but also make money selling vouchers that are both difficult and expensive to use.
However to my mind - without perhaps the knowledge of how the great unwashed masses think, it seems rather like the plan to get people paying 2 euros per minute for in flight phonecalls which flopped badly. People may be irrational but most people are not completely stupid.
Ryanair as a brand is about taking people cheaply and efficiently on short haul trips in Europe. The brand of Ryanair is being stretched too far - there is too much risk of a nacklash both from the USA where online gambling is very tightly controlled or other culturss which disapprove of gambling.