Firstly, ask the mods to change your original post to more general comments. It doesn't take long to find your address where your bikes are unlocked.
There are bike theives who frequent the forums.
Secondly. I would suggest that the almax would be worth it in one long length to connect all the bikes together and through a wall and ground anchor.
Additional to this I would put a heavy duty lock on each bike too – be this chain, or cable – from Oxford or alike.
Then, I would have a couple of additional locks threaded through linking the bikes together.
Finally, I'd remove the pedals from the bikes when they're locked up too.
Theives like it easy. One lock that may take a minute to get through is more attractive than three locks that take 45 seconds each.
Also try and keep locks 'tight' so that they can't be levered without damageing the bike.