It would be a bonus if the tweeters had their own channels. Then you can adjust the gain to taste, and probably use a filter (if your amp has it) to keep the lower frequencies off of them. Otherwise yeah, I would tether them to the front channels with either 'bass blocker' or other passive filters and go from there. I'd go with the lowest impedance (parallel wiring) assuming all components are happy with it (within power limits for speakers and impedance range for amp).
If you're really worried about how much power is getting to the tweeters, you might consider going with a series wiring rather than parallel. Bumping the impedance of the load like that should cut the power output from the amp. But I'm not a huge fan of running the same signal to my main speakers after getting choked off by running through the tiny voice coils in the tweeters...