Newclimber, it sounds like you will be having a lot of fun besides time in the mountains. If you have time, desire, and favorable conditions to get away to the high peaks on each leg of your trip, it will help some with conditioning and acclimatization for Whitney. However, I suspect most time will be spent being social at low elevations, so the keys for Whitney will be good luck with conditions, time spent on acclimatization hikes near Lone Pine, and going slow enough to keep your heart rate and oxygen levels moderate on the Whitney hike.
As far as Charleston, yes, it would be strenuous to summit and, if not melted out, potentially hazardous.
As discussed, condition dependent, but compared to other options:
-Onion Valley TH to Kearsarge Pass/Mt. Gould would be convenient, high, easy to moderate, and scenic with about a 45 minute drive.
-The end of Horseshoe Meadow Road would give several easy to moderate options that start high with about a 45 minute drive. It takes awhile to get to the best scenery on hikes here, but the drive itself is interesting.
-Meysan Lakes TH would be half the drive time or less, but starts lower and is more strenuous and rugged.
-Rock Creek Road would be a 1.5 hour or more drive, but would provide scenic, easy to moderate, high altitude, and highly traveled options.
-South Lake/Lake Sabrina area would be about a 1hr15 minute to 1.5 hour drive, but would provide scenic, easy to moderate, high altitude, and highly traveled options.
One more idea is to visit Death Valley NP on the way from Vegas to Lone Pine or to make the drive over from Lone Pine if weather is better there than in the Sierra. Scenery is great even while just driving through. Telescope Peak is the obvious choice for acclimatization purposes and ultra-prominence, while Wildrose Peak would be a quicker hike. If it isn't blazing hot out, Golden Canyon and Mosaic Canyon make for quick, fun, and scenic tourist hikes close to the main highway route through the park. Dantes View Peak is worth the detour if you happen to be heading from Vegas to/through Furnace Creek.
Happy Isles-Mist Trail-Panorama Trail-Glacier Point-4 Mile Trail makes for a great Yosemite semi-loop hike. Take the free shuttle bus if you find yourself far from wherever you parked. Renting bikes is a nice way to sightsee in the valley. Of course, you may have heard there is climbing if you are looking for that.