We are doing this tour on the 4th May 2009.Any suggestions, advice, must do's etc. We are staying in Vancouver for 4 nights on our own to pick up any missed opportunity's.Would like to also know any must do's in these 4 days.

Love Vancouver - one of my favourite cities in the world. I take it the obvious things are covered - Grouse Mountain and the scary suspension bridge, Gastown. I enjoy walking in Stanley Park - you could hire bicycles and join the throng.

I vote for walking the seawall in Stanley Park too - we try to do it when we go over to Vancouver. Be careful you don't go at 9 [am or pm? I have forgotten] when the 9 o'clock gun goes off. Queen Elizabeth Park is lovely, too. One of the chair lifts on the north shore is great on a clear day. Walk down Robson street and people watch. Or go to Granville Island.

Ah Granville Island and the food (there are quaint shops too).

Dr. Sun Yat Sen Chinese Garden
http://www.vancouverchinesegarden.com/

Granville Island for sure
http://www.granvilleisland.com/en/node

Most certainly Stanley Park. They have free hop-on-hop-off buses running through the park and the drivers give a pretty good commentary of what you are seeing.
http://www.city.vancouver.bc.ca/Parks/parks/stanley/
http://www.seestanleypark.com/

I bought a 2 day hop-on hop-off bus ticket and got around the city that way.

Please don't forget the following Vancouver attractions ...

Robson Street

Capilano Suspension Bridge

Queen Elizabeth Park

If you still don't have enough to do to fill your time, you can take a ferry to Victoria, and go right downtown to the Inner Harbour on a bus from the Vancouver bus terminal.

Thank you all for your suggestions.
We love to travel and experience what the world has to offer.

We were lucky and completed this tour starting 11th May this year. We had perfect weather but quite cold still. We couldnt get to Sun Peaks highway from Waterton as the road was still iced in. The sceneray everywhere was fantastic and make sure you go Goldleaf for the Fraser River Rocky Mountaineer as the scenery is just spectacular. Do as many optionals as you can, especially the day trip of bus up and train return through the White Pass from Skagway in Alaska. There was a good range of ages & mainly Aussies on the bus trip and not rushed at all.
Try and have an extra day in Calgary before the tour as the trip over is tiring. We went direct Air Canada-Sydney Vancouver. We also stayed 4 days at end of tour in Vancouver and had no trouble filling that time visiting mostly those places shown elsewhere on this thread. Getting around on the hop on hop off bus was easiest. Vancouver is in the middle of a building boom with the Whistler olympics in 2010, so make sure your hotel is not under renovation as ours was.
Hope you enjoy the tour.

You will love Vancouver ..... there is so much to see.