Well, now it depends on the ages, interests, and stamina of the people in your group...

The west coast of the Island is definitely worth seeing, but driving to Tofino is out in one day. Flying is one option, with a meal at the Wickaninnish Inn or a restaurant in Tofino.

For a one-day coastline trip closer to Victoria, rent a car (remember to drive on the right) and drive out along the southern coast of the Island to Port Renfrew. Stop at China Beach for the scenery and some tidepooling and the pub at Port Renfrew for a drink. Make a reservation and hit the Sooke Harbour House for dinner on the way back into town - it definitely lives up to its reputation for great west coast cuisine and atmosphere.

If you're into wining and dining, drive up into the Cowichan Valley and take in some wineries and a cidery on the wine route. Stop at the Crow and Gate pub for lunch or find a cafe in Cowichan Bay. Stop at a beach for the scenery and some petroglyphs. Take in a gourmet dinner with a view at the Aerie on the way back over the Malahat.

If the weather co-operates, you can take in a round of golf in Victoria before either of the above. I have some problems with all the building going on at Bear Mountain and the effect on the environment, but the views from the course are amazing. Check out Olympic View also.

See if you can find someone with a boat to take you out for a sail, also weather permitting. Although, some of the best racing is during the winter.

If you don't want to drive, take a whale watching tour from Victoria Harbour in the morning, then come back and take in the totem poles and exhibits at the BC Museum in the afternoon. Walk out to the breakwater and stop for coffee at the cafe or go scuba diving (don't forget the drysuit - the wather's cold). Or check out the schedule of The Malahat, the train that runs up the eastern side of the island as far as Courtenay http://www.viarail.ca/trains/en_trai_roch_vico.html. The schedule is quite limited, but the scenery is amazing.

With regards to bars, restaurants, etc. - if you have a business contact who has connections, a drink at the Union Club is a very Victoria thing to do. The Bengal Room at the Empress is an experience. For brew pubs, try Swans (great west coast art and craft beer), Spinnakers, or Canoe.

If you in any way, shape, or form end up at the Wharfside or somewhere like that (overpriced tourist trap with lousy food and questionable sanitation), I will deny that I ever gave you any advice or suggestions - be warned

There are lots of other good threads in this forum regarding spending the day in Victoria.