Caveat: I'm a one-year novice myself.
I've trained at both Ki Society and non-Ki Society dojo, and there is a lot in common at the early levels--the fundamentals of falling and rolling, the basic attacks, the basic responses, all very recognizable despite the style difference. So even if you know that you eventually want to end up with Ki Society, studying elsewhere will still give you a lot of what you need. It's all Aikido in the end.
(There'd be a certain amount of relearning. There are techniques for which I only know someone else's version, so I try to guess the Ki Society version, sometimes with ludicrous results. Sometimes you can take the direct physical push out and substitute a down-up-down movement--but sometimes you can't! Luckily my teachers have a sense of humor.)
I understand why other posters are urging you to talk with your sensei about this, but I don't know, personally, if such a conversation could be enough to make me feel safe. Three injuries to two newcomers in one class is a *lot*.
On a tangent, a word of advice: tie your hair up if it's physically possible. Mine is fairly long, and the first time I did a back roll on it I swore never to leave it loose again.