WELP. For the Forge world, we should send Akarth, obviously, and I suggest we go ourself too (be useful to get some hands-on experience with the mechanicus and, quite frankly, if worst comes to worst he's more important to the chapters survival than us, being our only techmarine if I've interpreted things right). Take an honour guard with us to the planet itself, not small exactly but no more than protocol would dictate (I'm not sure how many this would be), but have enough marines standing by on the ship we take (I'd say just a strike cruiser) to come to a total of 50 marines when the honour guard are counted, with a 3:1:1 split of Tactical, Assualt and Devestator marines. Just in case this little kerfuffle is more than we thought, y'know?
For Tarren, we should send Azakniel, with say 2 squads of assualt marines, 2 squads of tacs, a squad of devestators, some guys on bikes (say, 5 of them), and our librarian to screen for potential in the prospective initiates, not to mention possible heresy in the populace. That should be more than enough to deal with anything short of a warp portal and CHAOS!, so we should be fine there. Have him deal with whatever the problem is, then conduct the recruitment sweep.
As for Ancharon, have him draw up a revised roster for the initiate/tactical marine switch, with the assistance of Kaleth who should know who will work well together and what-not, and then work on plans for training the pdf forces.
The Apothecaries need to suggest any brothers they think would be suitable for apothecary training, as do our chaplain and techmarine for their respective disciplines, which they can do on the way to the planets they are being sent to.
Also, get mr slow-but-loyal to have a look-out for anything of note happening in the surrounding regions, and leave him temporarily in command in our absence.