Ame,
Using HC without being able to take care of the tank on a regular basis is out of the question. Autodosing is not the way to go either.
If you cannot maintain the tank on a regular basis you have no option but to make a low light tank. With or without CO2. Use mosses and crypts. No daily fertilization (but some peat + laterite in the substrate will be welcome for the crypts).
Here are 2 pictures of such a tank - only moss + a few crypts:
http://www.aquaticplantcentral.com/f...1_original.jpg http://www.aquaticplantcentral.com/f...2_original.jpg
The light should be no more than 0.5 watt per gallon. The first 4 to 8 weeks of the tank's life you may even leave it with just ambient light (but not complete darkness). After that the tank should be stable - you will be able to ignore it for weeks. Evaporation will always be a problem so use a glass cover over the tank. CO2 is good to have but will not be a disaster if it runs out.
It will be good if there's someone to feed the fish lightly on a regular basis - this will provide a minor amount of other nutrients, mostly Phosphorus, but with the low light that will not be a problem but rather a good thing.
And more details how to make a similar tank:
http://www.aquaticplantcentral.com/f...4&postcount=12
--Nikolay