Not recommended.
I booked my tickets one month before going to Venice. Unfortunately 50 minutes (!) before the visit of the church I got the email, that my order is cancelled.
Refundation of the service was immediate, but we had planned all the day in Venice to visit the Basilic on time and we were really disappointed.
In addition (probably because of conversion of euro) we got back lower amount of money then we had paid (the difference was about 8 euros).
Never more.