first off i am on your boss' side of this, viewpoint-wise. and we recently had a girl (with completely twisted priorities, imo) who had already worked with us once, then quit to be a sahm when she got pregnant. well she came back and has done it to us again. first she asked for six MONTHS maternity leave (ok in a perfect world that would be great for all moms but come on, be realistic!) then she gave her notice. (technically it was because her husband got this job that supposedly pays $100,000 a month, but since he doesn't even start for another two weeks and she already gave her notice i think she's an idiot, but that's my issue. that's not looking out for your family, that's being irresponsible and leaving your employer in a lurch for no reason. what if the job doesn't work out? what if something happens?? anyway...)
we ALSO just had to get everyone on a new schedule, and people are TICKED. but the thing is, you schedule your life around your job, not schedule your job around your life. that is key #1. IF you can honestly say that this is good for business or won't affect business, then i would go that angle. it sounds like it is a good business decision to come in earlier. but you will have to be sure of that. just keep in mind, to the company, business comes first, not your family. to them i mean. i am a mom first too, but if my job was not compatible with my family life, it would have to go. but to me making it work with my job IS taking care of my family. that job provides for my family so i will do everything earthly possible to succeed at that job.
anyway, i know i am rambling so i will stop with apologies. if you can sell this as a business decision (and it sounds like you can, between the other girl working that shift, and east coast business, etc) then approach your boss professionally. maybe even leave your family reasons out of it if you CAN, or save them for one of your last reasons for switching. good luck!