I am surprised he is not already baptized, I thought it happened normally 2-3 months after the birth. Would they announce it beforehand or at all? I'm not sure.
I think if all is well with the baby, you can have the baptism at any point in their lives. It has become quite a trend here to wait until the child is a bit older, so they can build some memories. My daughters were baptised in their father's church and since we at the time lived overseas, daughter two was 6 months and daughter three already almost 9 months old.. I have been to confirmations (which usually happens at around 13-14 yo) and several of the kids were baptised directly before the confirmation.
I used to teach a communion class for kids at the third grade level - children were not supposed to partake of communion in the Presbyterian church until they understood (at their level) what it meant. There were three instruction units and I added in baking the communion bread to the last unit. Since one of the requirements for receiving the sacrament was to be baptized, we occasionally had kids who needed to be baptized then and ditto when it came time for confirmation.
I was present for the baptism of a woman in a nursing home who did not know if she'd ever been baptized. That was the most poignant. The one that took the most physical consideration was a lady in her ninth month who was joining the church - there's no bending over the font either way.
Anyway, I think they are waiting until everyone is vaccinated and able to attend. While HM has not been present at all her great grands christenings, I think she'll want to be present particularly for August and Lucas. It's a time and a lovely reason for the family to celebrate.
Here's a question for our Anglican posters, does the COE recognize baptism in other denominations? I'm asking because I was wondering if the baptisms could be done at Balmoral?