Help quitting as a Nanny.

I am going to quit my job as a nanny soon and I would really appreciate some opinions from those who have quit, moms, other nannies, or anyone who feels like giving advice. I have working for this family for about 7 months now, primarily watching a baby boy since he was 5 weeks. This family has been very kind to me and I am not quitting because of anything they have done. I am currently studying to become a Pharmacy Technician and am engaged. I really need to be able to start looking for a more permanent and high paying job in the field that I want to work in. My plan is to tell her on the last day of this month that I will be done working there on the last day of May. That gives her a month to find someone new. Is this enough time? I've been thinking that I may say I am available as long as she needs me up until the last day of May that way she doesn't feel bad if she finds a replacement before the month is up. I really need some opinions on if this is a good plan and some ideas on what to actually say to her when it goes down. Thanks in advance!