I went to Tanzania several years ago about that time (pretty sure it was November, but might have been October). I loved it. Yes, it was hot. But not unbearably so - and I hate hot. We did Arusha (there's a park near there where we walked with an armed guide to a beautiful waterfall), then Lake Manyara, then Ngorongoro. Great safari. We also spent some time on Zanibar and I recommend that, too.