Current temps are 80f in the basement and 90f upstairs so I suppose the move is to either chill it then let it warm up to 80f in the cellar or just empty out the kegerator and ferment it in there in the 70s.
You have a kegorator but no A/C? I hafta commend you for keeping your priorities straight!
I think you can get by without utilizing your kegorator, especially since you don't want your other kegs sitting around at 80F-90F.
I know there are differing opinions, but I wouldn't start fermentation above 70F. Saison yeast does and will give off hot alcohol/phenols if you start at high temps (plenty of examples in any homebrew comp or festival).
Chill to 65-66F, aerate like crazy and pitch your healthy starter. Make an effort to hold that temp for the first 24 hours, then let 'er rip. As fermentation subsides (airlock activity slows), bring it upstairs and wrap the fermentor in a blanket to hold the heat in so the yeast can finish out.
The 'control' for the initial fermentation doesn't have to be elaborate. Run a Google search for swamp cooler, wet t-shirt/towel with fan, etc. You can also use the kegorator for the first 24 hours of fermentation, wrapping the kegs in a blanket while they're not in the fridge.
As far as Lacto:
Lacto will work slowly (if at all) if pitched after fermentation. If you pitch lacto before sacch., you'll get acidity in days rather than months.
Let me know when you're planning on making this one and help you navigate the process.