Not sure why Meghan would need to be there as she has nothing to do with Invictus, however much she likes to insert herself into it when it suits her.
RAVEC did say that Harry and his family's security needs are under constant review, so if he is deemed to require security, it will be provided. Which is very fair and reasonable. This whole thing has been a bit of a farce. Not only has it used scarce public resources, it's going to end up costing him a vast amount. Also, it has really drawn attention to his security, or lack thereof. That's a really dumb move. There's a reason why security matters are considered confidential and not a matter for public discussion.