Late September or Early October is fantastic weather. I went on the 1st week of Oct. If you are bringing your elderly parents who cant do alot of walking and its a 10 day trip. I recommend just do Kyoto-Osaka. Below is my itinery.
Pros: My itinery is for convenience where walking is minimal as all attractions are along the flow, minimize time wastage.
Cons: My hotels are all less than 5mins walk from main stations or attractions as I hate to walk alot due to leg problem so it might be 15% more expensive. But its really damn worth it to stay at a more convenient location. Since you seldom go for holiday trips, why not do a good one and spend abit more on convenience.
Day1-3: After landing at Osaka Station, take the airport bus direct to Kyoto Station (
http://www.kate.co.jp/en/). Kyoto Station is a bus terminal + train station. From the kyoto station, the bus terminal infront of it has all the english signs that tells u what bus to take to different attractions. Take the bus to Arashiyama (google arashiyama). Spend 2 nights there. Arashiyama has many attractions that are walking distance to each other. (5-10mins walk). At Arashiyama, you can visit Togetsu Bridge, Bamboo forest, Kimono forest (beautiful at night), Monkey Park, take the Sagano Scenic Railway from the LOCAL station (Arashiyama has 2 station, dont go the wrong 1), take 4 stops and then a 1 HOUR traditional boat ride back to Togetsu Bridge (my trip highlight). Visit the many restaurants and food opposite the Togetsu Bridge. Try stay at the hotel near to Togetsu Bridge.
Day 1: Try finish Togetsu Bridge, Bamboo Forest, various attraction along the way to bamboo forest.
Day 2: Do the Sagano Scenic Railway + 1hr Traditional Boat Ride back to Togetsu Bridge (this part will cost you first half of the day alrdy), Have dinner before 7pm as all shop close by 7pm. Only convenience stores are open at night. So after dinner, ard 8pm then go Kimono Forest.
Day 3: Do Moneky park in the morning then late noon go back Kyoto Station.
Must eat: Taisho HANANA in Arashiyama, opposite togetsu bridge and then a further 2min walk (Go before 1pm else long queue or sold out).
Day 4-7: Take a train or bus from Arashiyama station back to Kyoto Station and spend 3 nights there. I stayed at hotels just opposite the Kyoto Station. All buses to all Kyoto attractions can be taken in Kyoto Station. Kiyomizudera is a must go in Kyoto. U can ownself decide where to go. There are 15-16 attractions to choose from at Kyoto Station Bus Terminal. I recommend 1 day do 2 is enough. (Signs all in english. Damn easy to travel around).
Day 7-10: Take train from kyoto station to Osaka. Try stay at hotels opposite Dotonbori. (I recommend RED ROOF PLUS HOTEL as its opposite a shopping street and 2min walk to Dotonbori and infront of hotel has a underpass that leads to the subway for easy traveling). Visit Nara park etc from Osaka.
Last day, take cab to Osaka Internation Bus Terminal (Namba OCAT) (Its 5min cab ride from RED ROOF PLUS HOTEL, not ex) and take airport bus back to Osaka Airport. Try to reach Namba OCAT 15mins earlier as this building quite big, need to find the counter to buy the airport bus ticket.
http://www.kate.co.jp/en/timetable/detail/OC