I have the Canon A70 and just used it on our Christmas trip.
I have two 256MB cards and two sets of 2200MA NiMH rechargable batteries. At the highest resolution and the superfine setting, I get 156 shots per card. If you run video clips, they take up lots of room if you do the 640x480 setting. The clips at that resolution can be no more than 30 seconds. You can do 3 minutes each at the 320x240 setting.
I found that I would pretty much fill up both cards every day and pull them off every evening or even during the afternoon break back at the resort. To make pulling them off easier, get a CF card reader for your laptop (less than $20). This lets you drag and drop the files into your folder. Windows XP will transfer them into a picture folder, but it is slower as it will rename every file. If you go into the camera menus, turn off File No. Reset (Menu/Tools/File No. Reset). This will keep incrementing the filenames up to 9999.
I saved about 1000 pics from a 17 day trip and about 30 video clips. I took more, but deleted in the camera or on the laptop if I didn't like them.
You might want to bring a tripod or unipod for fireworks and night pics. I carried a small hiking tripod that is only about 8" long and fit in my fannypack. It has a strap so you can strap it to a pole or rail for a quick mount shot.
Zurg has a page of tips and sources
here.
Good luck and have fun with your camera.