Wow... so many options. It is really hard to give a good answer without knowing what the domains are and the differences in the domain names themselves, but here are a few thoughts.
If the domains provide some distinct differences, whether that be target audience (grandmaroadbikes.com) or branding (ZippzRoadBikes.com) then I would start with the cross domain canonical tags. There are many sites that stand on their own while using cross-domain canonicals and maintaining their own brand.
How similar are the domain names? If the domains are too similar, and unique branding can not really be achieved, then I would consider the consolidation. My gut reaction as an advertiser is to stick with the easiest to say and type. I assume the domain being marketed offline wins that prize. I would focus on promoting that domain. Further, many people will loose a bit of trust if they type in www.AdvertisedDomain.com and get www.DomainUnAdvertised.com. Plus you don't want to cause brand confusion.
