I have a bit more info:
Food: Omega seems to still be the best as it has the protien and nutrients that bettas really need. It comes in pellets and flakes. Bettas like variety, so both work. If you use pellets, try soaking them in some water taken from the tank for 15 minutes so they will be soft and gentle on your fish's stomach. Blood worms are treats, but too often and your betta will miss out on good nutrients. Anyway, if you get the flakes they are easy since they break into smaller pieces- just gotta watch them and make sure you clean the water frequently.
To add to that.. Omega is a very great brand to feed... but being as small as she says, she should look into live foods to give the extra oomph that a tiny baby needs for growing. The diet is one of the most important things at this stage. Freeze dried is not something you want to offer them at this point.
Another note: soaking food is a bad idea, as that their processed foods start to leach out their nutrients as soon as it hits the water- so soaking 15 minutes will give the baby even less nutrition then what it's getting if feeding simply pellets.
Cleaning: Difficult... try that amonia alert I talked about earlier. I think the general rule was 1 50% change and one 100% change per week for a gallon...
Cycling: Since your betta cannot go into the larget aquarium yet, have you thought about using the time to put your tank through the nigrogen cycle? http://www.myfishtank.net/articles/fishless-cycle/
You can use a variety of methods as well as one that uses the amonia alert I told you about before: http://www.csupomona.edu/~jskoga/Aquariums/Ammonia.html
Keep in mind, a tank below 5 gallons is very difficult to cycle, and if you manage to get it cycled, it won't be stable as the surface area is too small for the bacteria to hold one properly.
You've got the time, might as well cycle the tank.
Filtering: Yep, the pre-filter sponge is great! I've also placed one over an airstone so the water is very gentle but still oxegenated and filtered.
Plants: Try to see if you can get some Java Moss. Java moss helps keep the water clean, so your fish has less amonia to put up with between cleanings.
Heat: Sounds like you got that covered.
Toys: My betta adores this: http://www.amazon.com/Zoo-Med-Floati.../dp/B0027ITKBS
Decor: Make sure you drag nylons across anythign you want to put in the want. If it tears them, it'll hurt your fish. Bettas like to hide sometimes (making the cups in the store all the more terrible) so if you get anything with a hole, make sure your thumb fits through so the betta won't get stuck.