Totally doable! You'll know how easy to take it during those in between days based on how you feel after the first one. I'm usually fatigued right after a race, but my recovery rate is pretty quick - I'll do a long ride or something the day or two after. Like Colby said, don't do anything too hard the day or two before the second race (just like you wouldnt before any race).

It really just depends on what you mean by not being "prepared" for the race. This is my first season doing tris, and my swimming sucks so I never feel "prepared" - I should swim a lot more than I do to be better prepared. But I am physically capable of doing everything, and I don't come out feeling any more tired than I do on long, hilly ride. Usually, I'm more mentally exhausted from being amped up than I am physically