cheapest to book via your travel company, have been to bansko and pamps and local instructors were v good, havn't been tp Boro before but from this site the same seems to apply. As beginners it should be fine. Learned to ski 2 years ago and Love it ! you will have a fantastic hol, be prepared to laugh a lot!
If you have booked through a tour operator use them for a package, much cheapness.
If not I believe Fiona on this site can help, don't know her though. leave a post for her.