October is a good time to be on safari in Kenya. There is still some migration and river crossing activity in Kenya, mainly crossing from the Masai Mara back into Tanzania. Although this is seasonal and changes every year.
Be aware that the Masai Mara gets busy, especially during migration / river crossing seasons. Although October is not a peak month, you can still expect to see lots of other tourists in the key locations.
If your budget allows consider staying in a private conservancy, where you'll get a much quieter experience – which is better for the wildlife too.
Alternatively if you're not dedicated to seeing the migration there is much much more to Kenya beyond the Masai Mara. Places like Samburu National Reserve in Northern Kenya or Tsavo on the Southern part are quieter.
