The breakfast situation might work differently. I have read about people being seated for Minnie's before official park opening even though they didn't have early entry. You're supposed to be able to let a CM know (designated entrance gate perhaps?) that you're there for the breakfast and then you get taken to it. Anyway, we have never tried this ourselves, but I'm sure I've read accounts of others who did this. So when you call Disney to change your reservation, you should explain your situation and ask first if it's necessary to change instead of just assuming. I figure it never hurts to ask, and you might find that your original plans will work out.