Other than the date, there are no other confirmed details as yet. Very difficult to plan at this stage, unless a venue already gives specific information, such as the performance mentioned by Globaliser. But for now, do not take lack of notification as meaning there will be none. Things will change.
Important to consider the impact in central London and the rest of the country separately. There will be extensive disruption around the event (so the Westminster area surrounding the Abbey and Buckingham Palace), with road closures, other transport disruption, such as closed stations, and restricted access (some areas may be ticketed) and large crowds. London generally absorbs large events very well, but this is literally a once in a generation occasion.
Elsewhere, there will not be the “mark of respect “ aspect that accompanied the late Queen’s funeral, but there will be local celebrations such as street parties and it is likely that some (who knows how many) businesses will close or limit their services so that their staff can at least watch the events of the day. Public transport will be running. I would expect Royal sites across the U.K. to be closed.
For now, I would be reconfirming hotel reservations and any already made arrangements. Make other plans, but keep in mind that they may change. Keep checking back!