Osaka to kyushu

Hello,

Our family will be arriving in Kansai airport on December 22. If we purchase the meet and greet service from JR pass, will the agent help us to activate our passes from December 24 and make all reservations for all our planned trips using the JR passes?
Our family will be traveling from Osaka station to Kyushu. Our plan is to travel from Osaka to Oita station, where we will stay for one day.
The next day we will travel from Oita to Yufuin.
On day 3 we will continue From Yufuin to Fukuoka (Hakata)
Finally we will return to Osaka station from Hakata

Is there a link for us to plan out our trip so we will know exactly the routes we will need to take using the JR lines? Is the only supplemental purchase for the Nozomi line via the ticket counter? Thank you for your help.