Unless you've got a specific reason to avoid the Water Bus, it's a great leisurely trip and stops right in front of the Danieli. It does take a bit longer than just getting a taxi, but it's also a ton cheaper (if that matters to you). I think the best deal my group came up with was some form of a group ticket that worked out to just a few Euros each (don't remember exactly what it was right now, but I'm sure you could figure it out). We weren't at the Danieli (but did eat there) but stayed just a block or two away.