No. No. No. Don't work at this place. Any manager that is hiring on a new grad in a float position should have her head examined. You need to be working in one stable position where you can be oriented and complete your training as a nurse. Learning to handle the work in one intensive care unit will be challenge enough, let alone two other units. No. Don't do this. Take a position in only one of the units if you still want to work there and ask for a "no float" promise, especially as a new grad. Don't let them bamboozle you into taking this on. They are taking advantage and using you.
I can tell you exactly what will happen to you. You will start off assigned to one unit, probably Peds (they have to do that for accounting and payroll purposes), and then every time they need someone in NICU or PICU you will be the one they send. They will start you out in Peds because you are a new graduate, they'll say, and you need some general experience first. If they can't offer and promise you a definite intensive care training program do not take this float position.
Get it in writing too. Ask, or they should give you, a written offer of employment that clearly defines what job position they are offering and what training they are willing to offer. That is how it is done these days.
I was a head nurse of a medical unit in a large city hospital. I was also a member of their new graduate nurse committee and it was our task make sure the new grads were transitioned into their new jobs in a special orientation program. The ICUs are very special places and we offered a 6 month training period in just one of the ICUs alone. Our orienting graduates were not to be floated anywhere for at least 6 months. If your new employers can't do that, look elsewhere. If you need the job right now, stick it out, but look elsewhere. You can quit without giving notice anytime during your probabionary period (and they would deserve it, too). It's jobs like these that get nurses off to a bad start and lead to them becoming disillusioned and leaving the profession altogether.
Sweetheart, you may be finished with nursing school, but your training is not over yet. Any employer who is not willing to understand that you are still a tender-roni and need special handling isn't worth your time. Please keep looking. I don't know whether you are an A.A. or B.S.N. grad, so I realize that may make a difference, however, pick your first job experiences as carefully as you made your choice about schooling.
Floating is not as romantic an idea as you are thinking. Most nurses hate to do it. No one likes being pulled off their regular units where they feel comfortable to work where there is obviously a shortage (cause that's why you got floated!). Floats have a bad reputation because they are perceived as not having the same dedication as the regular unit staff. Floats do not do the "little things" that tend to be done by members within a unit. Supervisors and staffing coordinators see floats as bodies to fill in the staffing holes. Some of the nursing staff will like you because you're the one floating instead of them. They won't particularly like you for all the other reasons I just listed.