Timers are the best thing to use to turn on lights and turn them off.
Undertank heaters are unnecessary for dragons and can be potentially harmful. I wouldn't use it at all except on belly warming reptiles like snakes. Basking overhead lights are better for dragons.
It would be best to arrange for a reliable friend to come in and feed your dragon once a day at least, twice a day at best giving the age of your dragon. Getting them to eat pellets is also a great alternative. Getting silkworms to use as food wouldn't be a bad ideal as you can leave a dish of silkworms in the cool part of the cage with silkworm food. The dragon will eat the silkworms when he is hungry (I don't think he will eat them all as mine will leave one or two if he isnt' hungry when I toss in 4 or so before his regular feeding time if I know i won't be there to feed him). Since silkworms are not big wonderers like crickets, they won't go very far or hide.
Leaving a large quantity of greens and pellets near or in the cool section of the tank should last for a weekend (assuming you feed them friday, come back on Sunday, they may only miss two to four meals). The fact this is ever weekend best to use pellets or a friend to ensure he eats regularly.