I build, rebuild and true spoked wheels as part of my work. Where there are just a few slightly loose spokes, up to about 1 turn on each of the culprits should do the job without causing any problems, however, I would deflate the tyre first to prevent the nipple head damaging the rim tape and possibly the tube. The rear swingarm and the front fork legs make remarkably good 'jigs' and I have corrected offsets and distortion problems in situ on numerous occasions. If you have any doubts, mark the loose spokes with coloured electrical tape, tighten say half a turn at a time and then spin the wheel to check. At the very worst, a few thou out of true is better than having slack spokes.
If the spoke nipples need a few turns, I would be getting the tyre, tube and rim tape off, to keep an eye out for any spoke ends poking through and deal with them as required.
B.W.