Reserving seats on JR East Shinkansen

Hi, I have a unique question which I have not been able to find the answer on the web.

I will be buying a JR East Tohoku pass in Singapore and will exchange the voucher for the pass when I land in Tokyo in end October. However, I would like to reserve seats on the Hayabusa Shinkansen to Aomori at least 2 - 3 weeks before I land in Tokyo. This is to ensure that my family will definitely have seats on that particular date and time (I am just being careful!). Can I reserve the seats on the JR East website before I even land in Tokyo? I tried reserving seats on the JR East website and it appears to allow me to do it (I did not confirm as I was testing only). If I proceed to confirm the reservation, will the JR office honour the reservations when I exchange my voucher for the JR Pass on arrival? I am a 1st time user of JR Pass!

Thank you for any help.

- JR-East Train Reservation
- - Top
https://www.eki-net.com/en/jreast-train-reservation/Top/Index
- - Agreements for member registration
https://www.eki-net.com/en/jreast-train-reservation/member/wb/Regist/U...
- - User Guide: Usable periods / times
https://www.eki-net.com/top/tr/guide/reserve/timein.html

This system requires your credit card of any of the following brands.
: VIEW CARD, JCB, Visa, MasterCard, American Express, Diners Club.

I recommend
you check whether the system really accepts your credit card,
using tentative data.

You can buy your JR-East pass on this website.
If you purchase your pass somewhere else,
you cannot try your seat reservation there on the day before boarding.

Your Shinkansen seat can be reserved
from 10 a.m. of the day one month before your boarding day.

Enjoy your trip!