JR Kansai Area Pass & Koyasan Heritage Pass

Planning a trip to Kyoto for 9 days and will be staying some nights in Koyasan and Osaka.
I will be arriving at KIX around 1430 (not sure how busy immigration but I predict it will be about an hour or so). I was reading about the passes and it looks like the best pass based on my itinerary is the 1 day JR Kansai Area Pass and the Koyasan Heritage Pass.. I understand the JR pass has to be purchased on the day of my arrival but would it be wise for me to purchase the heritage pass on my arrival as well? or should i purchase it on the day of my travel to koyasan?

My itinerary
Day 1- Arrive KIX go to Kyoto stay Night
Day 2-4 Kyoto area (Nights in Kyoto)
Day 5 Himeji and Kobe (Night Kyoto) *Activate JR Pass
Day 6 Koyasan (Night Koyasan) * Use Heritage Pass
Day 7-9 Osaka (Day 8, day trip to Nara)