JR Pass and seat reserved related

Hello,
My trip starts from 25 Nov to 8 De., I arrive at Kansai Airport at 8 am 25 Nov. I plan to use 14-day JR Pass National wide and would like to turn exchange order to actual JR Pass in the Kansai Airport and start using it to go Hakodate (Hokkaido) as schedule below:
1/ Kansai-Airport Station to Shin-Osaka Station:
Haruka 10 Limited Express Kyoto: 9.16 am - 50mins - 10.06 am
2/ Shin-Osaka Station to Tokyo Station:
Tokaido-Sanyo Shinkansen Nozomi: 10.33 am- 2h30m -12.57 am
3/ Tokyo Station to Shin-Hakodate-Hotoku Station
Tohoku-Hokkaido Shinkansen: 1.20pm - 3h23m - 5.47pm

However, the route from Tokyo to Hakodate must be reserved in advance. Is it okay if I make a reservation just about 4 hours prior train's departure time when I active JR Pass at Kansai Airport? Or must I change my schedule to go to Hakodate in the next day to make sure the seat can be available to reserve?
Thank you so much for your supports,
Regards,
Thuy Anh Nguyen,

1) Nozomi is not allowed.
2) Yes, you can reserve Tokyo to SHH at KIX.

You may better use Jorudan's Rail Pass search.

https://world.jorudan.co.jp/mln/en/japan-rail-pass/?p=0&xpd=1&from=Kan...

Note that Shin-Hakodate-Hokuto is just a railway station: There are not so many shops/restaurants/sightseeing spots. You may want to travel back to Hakodate which is about 15 min train ride.

https://world.jorudan.co.jp/mln/en/japan-rail-pass/?p=0&xpd=1&from=Kan...

Thank you guys so much for your feedback.
About Osaka-Tokyo route better I should change from Nazomi to Hikari to cover by JR Pass.
My last station actually is Hakodate Station which I forgot to describe in details.
Once again thank you so much.

Early afternoon departure from Tokyo to Hakodate are not usually the most crowded departures; so I have the feeling that it won't book out, and you should be able to make seat reservations on the day. If you are a larger group, then you may possibly not all be able to sit together, though.

In the unlikely case that the train is booked out, note that often only the Tokyo-Sendai portion is booked out. In that case, you could take a different train, such as a slightly slower Yamabiko, from Tokyo to Sendai and ride the Hayabusa from Sendai to Hakodate.

Thank you Uji for your support. I will keep in mind your advice.