I would not use a feeder block.
If you have long enough before you go get them good and fat now .
Feed heavy and do extra waterchanges .Then stop both day before you go..
The blocks are not real good and just for math 2 one week blocks will not get you 2 weeks of food over 2 weeks but 2 weeks worth of food over 1 week..They dissolve the same rate...I would worry about feeding and not changing water? Especially an uncontrolled block or 2..
Most have no issue with 7-9 days of no feeding..Maybe you could get someone to come over just once in the middle? Friends always screw up friends tanks so all you have to do is put as much food as you want fed out for them and that is all the can feed.Many over feed the 'hungry looking fish'..
If water doesn't get changed or refilled from evap I would offer a lot of food..