Booking seems to be fairly easy using LifeMile website and the inventory seems good. The booking would be Star Alliance booking so if things go wrong, the airlines with which the booking are done and star alliance should be able to handle things.
Hopefully you won't have any IRROPS but the couple of times I have run into issues, the carrier (TG) just punted on the problem and I had to go back to the airline whose points I used to purchase the *A ticket (UA) to arrange alternate flights, etc. Have never had to deal with Avianca so can't comment specifically but definitely something to keep in mind.