You are right to be nervous about soldering directly to Li ion cells. Very bad (i.e., Ghostbusters-bad) things can happen. If the cells don't have tabs already spot-welded to them, you can add some yourself. Rigging up a kludgy spot-welder for this purpose is not hard (main ingredients: power supply, and BFCs -- big, fat capacitors). If you decide to go this route, post back. I can provide you with more detailed instructions on how to construct one (and how to practice non-destructively before you work on the actual cells).