Watching your aquarium is a good practice, because you will be familiar with how your fish act and will be able to spot if something is amiss.
Tiff is right about the silver dollars, they get huge, and also prefer to be in larger schools.
Doing regular water changes will not hurt the cycling process. There will always be an ammonia source in your aquarium because the fish excrete it through respiration. Right now your biofilter is still establishing itself, and the bacteria hasn't colonized the tank yet. This doesn't happen overnight, and sometimes it can take a month or longer. However, not doing water changes will allow the ammonia to reach toxic levels, which will do serious damage to your fish. Your tank will still cycle with regular water changes, even with daily water changes.
A 5g is fine for a betta. If he's not currently squabbling with the guppies, then they all should be fine in the 5g. Some bettas are more mellow than others, and usually the only problem is other fish nipping at the betta.