IF you have the time, go to Mt Kenya first and acclimatise...Realise you may be limited on time, money etc.
Plenty of chance to get local guides.
I did it this way then organised my own guide for Kili'.
I remember on Kili', that I had a time limit of 5 or 6 days to get up there, which was crazy considering the altitude.
In Nepal, you take a couple of weeks to get to that altitude...slowly....
Altitude affects everyone differently; no way of knowing until you get there. The one thing that does work well tho', is, if you can take plenty of time to acclimatise, drink plenty, (even if you aren't thirsty), and don't rush.
"Pole Pole", as the locals will tell you!!!