Hi,
When I go away, I tend to do the following based on the duration of the time away:
1. Do several large water changes prior to leaving.
2. Feed the fish some nice live food if possible and feed well so they have some fat reserves...
3. Lower the light duration to about 6 hours total.
4. Ensure your c02 bottle is full and will not run out while you are gone. You can leave the c02 on, just adjust the timer to coincide with the new lighting schedule.
5. Clean your filters and sponges a couple days before you leave to ensure they are running optimally.
6. Just before you leave, fill the tank to the brim for evaporation. Making the room cooler will also help lessen the evaporation. If you have a sump, fill it to the max level.
7. Dose some extra ferts the day you leave. The overdosing will NOT harm anything.
If going for more than 3 days, I usually have someone at least come in and sprinkle some food and refill for any evaporation loss.
I have gone away for 2 weeks and my buddy and his daughter (who know nothing about fish) were able to follow detailed written instructions on feeding AND dosing, plus filling the sump when I had one.
Don't forget to leave a contact # in case they have questions.
Hope this helps.