Ah, rally point like that. Sorry for being daft. The home colony or location of the fleet's lead ship, yes.
If you want to be sneaky, you could pick one ship, a lowly escort, for instance, as the rally point. You make this the lead ship in a new fleet by doing a right click option, or having it as the only ship or first ship to be added to the fleet. You move this ship to your super secret location rally location in the middle of nowhere, and wait. New ships built which belong to the fleet move to their escort leader. In the tips-thread on this forum, you can see a tip to use a cruiser as the rally points for your transports.
I would keep an eye on the first new ships to see that they bothered to grab fuel before they leave, if you try to have them go away when they are new. You may be out for a slow move if the station runs out of fuel while they are built, for instance.
Notice another thing with this behavior. Your fleet is in a hurry to get going, but one ship is out of fuel (they ran their refueling point dry). Giving the fleet an order will give the order to all ships. But fleet ships that are "done" will go to their leader. So order the fleet on their way, and select the low fuel ship (you see the fuel level as the green bar in the fleet box when selected), and give them individual refuel orders. They will refuel and follow. This is also useful even if you don't move, as you may not want to give the fleet another refuel order and clog the poor gas mine with 30 ships doing yet another docking to top up. One play style of mine makes this relevant. I leave empty troop transports on auto outside fleets to gather their troops from... somewhere. Every now and then I filter my troop transports, and add the full ones to a new fleet (say hi to Invasion 2, 3, 4, north, whatever). I ask this fleet to move to my wanted location. But the ships are all over the place, and may not have enough fuel to reach that location. So After telling them to typically refuel at my given point, I give the stragglers single orders to refuel first.
And yes, the Atuuk does not have the best commandos in the world. I am playing with them just now. You can see their strength in the troop list (or when viewing the troops on a location/ship). I think "standard" strength is about 10k, while the Atuuk are 5750 or something when recruited. So if you typically want 2-1 when attacking, the Atuuk is 4-1. Also, troops that win combat gets stronger. So it may be a good idea to watch who are your crack troops, and not pick which 10 transports will attack their home world quite at random. In my current AAR on trying to let the crazed Atuuk AI do diplomacy for me, I now have one lowly atuuk troop that has passed 20k strength, and several are closing in on that level.