Fishy Holiday

Don't use a block. People have been known to come home to a tank covered in a layer of white and a lot of dead fish. Not all blocks are this bad but I still wouldn't risk it. Some of them are plaster of paris with some food inside, hence the white blanket.

The conference in September - will there be anyone to look at the fish in the QT while you weren't there. Not do anything but just look at them and contact you if they looked iffy then act on your instructions? You could them put them in your main tank as soon as the 2 weeks were up.
Will there be someone to feed the fish for you? If there is, make sure they understand how much food. If necessary, buy one of those pill dispensers with a compartment for every day and put a day's food in the relevant compartments. If you don't trust the person, hide the food tubs so they can't give the fish any more.


The October holiday - you are going away mid October so if you put the fish in the main tank at the end of September they'd have a good 2 weeks after quarantine before you left them. That means you'd have had them a month so they should be OK to leave.
As for feeding, 2 weeks is a bit long to leave them without food. A week to 10 days is fine. I would definitely test the automatic feeder and if it proves OK, use that. Two things to watch out for are the feeder dumping the whole lot in at once, and dampness ie water vapour coming off the tank, getting in and making the food tacky so it won't come out. Maybe put less food in than you normally would feed and programme it to drop food in every other day.

Do a big water change before you go, and again as soon as you can after your return.

And enjoy your holiday.