Please Help..

Three people traveling (very flexible) YYC to Budapest (via LHR).

I have Aeroplan miles for 3 bus class..but no chance apparently for ACTUAL Bus class booking.. But seems I can get Two w/o big problem.

For third - to bring her to bus class.. Short of just paying $6,300, what is best choice:

a) buying ticket (non Tango?) and wait listing?
b) use aeroplan for mixed J/Y bus class reward ticket and waitlisting?
c) use aeroplan to buy economy and keep waiting to see if seat opens up and change to business class?
d) other option I haven't considered.

I have no status SE, E, etc..

Thanks for any advice!