Different port of entry for parents & child

Hello Daniel-san,
We will be visiting Japan in a month. While my partner and 1st child and I will arrive in Osaka from the US, our 2nd child will be arriving in Tokyo with friends from South Korea. We plan to take the train from Osaka to Tokyo to pick up our 2nd child, and then continue our trip all together.
The JR pass rules for online purchase states that "For children who do not have their own credit cards, the JAPAN RAIL PASS can be purchased if the itinerary is the same as that of the person who is making the payment." We'd like to know if this is possible:
- I purchase 4 passes with my credit card - I note Osaka as our planned port of entry (which isn't true for my 2nd kid, but I can only enter 1 port of entry online) - We have the same start and end dates for the 7-day pass - 3 of us pick up our passes at KIX airport, Osaka - On the start day, we take the train to Tokyo - Our 2nd child arrives in Tokyo on the start day, and we pick up his pass at the train station So our child would never travel without us, but we would have 1 train trip without him, and his port of entry (and therefore the temporary visitor passport stamp), would be from a different airport. Is this acceptable?
Thank you so much!