I believe I found a solution to my problem although its more of a hacky work around however at least it works...
Basically host the LAN Secops game as you would usually but only with the host in game, the AI will then take up the other slots. Once in game the helicopter will land safely with AI and host, then invite the other players to join who will take on either empty slots or an AI player.
Voila! - You'll then all be in game and in the same squad.
- Host LAN Secops game with only the host and AI.
- Wait for the helicopter to land safely.
- Invite other players to take over AI and empty slots.
- Enjoy Secops over multiplayer!
Like I said this method isn't exactly perfect but it gets the job done. If anyone else has any other methods or indeed better ones then please don't hesitate to give your answer!