Can I add extras after I buy the pass?

Hi guys! I am hoping to get some answers before buy my tickets. My husband and I are traveling to Japan and will arrive 10/12/2024 and while JR Pass will allow me to buy the tickets now (and will wait until July 30th before sending them to us)...and I am considering getting these bought now, just to get them out of the way.

However, I wanted to also secure a pocket wifi and a meet and greet session, but these are not available to be chosen out as far as we are still.

Can these be added on at a later point or should I just wait until the end of July to get the tickets?

Thank you!