Go with adjustable heaters. I do not find the mini ones to be very effective as far as heating goes, and the temperature will still fluctuate with the room temperature which is very stressful on the fish. I always recommend the 25 watt visi-therm stealth because it is VERY reliable and will last forever without any malfunctions.
Live plants are good.......BUT, you need the proper lighting, fertilizers, etc. There are a few easy to grow plants such as java fern and java moss, but I've never had much luck with them other than that they didn't die (but they didn't look good either). If you're on a budget and looking for a low maintenance tank, I recommend some silk plants. They look good, require no upkeep other than a scrub every once in a while, and last fairly long.
When you bring your fish home, you will need to acclimate him to your water. First, float the container for 15 minutes to let the temperature adjust. Then, remove 1/4 of the water and replace it with the new water. Continue doing this ever 10-15 minutes for about 45 minutes to an hour, but make sure that your container has an air hole during this period. Then, pour out as much old water as you can and dump the fish into the tank. Because he has been properly acclimated, he shouldn't show any signs of shock although he may still go and hide.
As for the weekends, your fish will be fine without food. How often will you be leaving? Every weekend?
A big thing to get out of the way before you get your fish is whether you will have your tank cycled or uncycled.
Personally, I would go with cycled because it requires smaller water changes but some people like uncycled... it's all a matter of preference.
Also, your betta will be just dandy without food for two days. Whatever you do, do NOT get suckered into those feeding blocks... they will only pollute the tank, posing a way bigger risk than starvation to your fish.
also don't forget to pick up a water treatment solution- unless you were planning to use purified bottled water. tap water has chlorine and fluoride and other such harmful additives that are bad for fish- you need to neutralize it with a with a water conditioner.
When you buy a betta, a lot of the time they come in a plastic cup with air holes. When you get home, gently set the cup on the surface of the water. It should float on its own. Be sure the fish is still able to get to the air, that is extremely important. You may want to watch it to be sure it doesn't tip over or sink.
If your fish comes in a baggie (my male did) then you can float the bag in a similar way. Again, you must make sure that your little one can reach the air while he adjusts to the new water/temperature.