Dear capwrite,
In my opinion it is remarkably clever of you to give the customers the option to buy with crypto. I mean, they do not have to but they can, and it is always nice to have the freedom of choosing whatever you want - in this case it is the freedom of being able to chose how you are buying certain products (which currency you are using).
Customers who are supporters of a specific coin (or specific coins) have the opportunity to actually use and support this coin.
The only possible problem what comes into my mind, is the volatility of a certain coin. Although right now the whole market is bullish and nearly every coin will gain to the upside in 2018 (and 2019 probably too).
So maybe you should only accept trageted and established coins.
All the best,
Gandalf The White