Lily did not consciously plan for anything. She was just defending her baby.
A lot of people (myself NOT included) are calling it a sacrifice, but that was not her intention.
She was not thinking about herself at all.

Dumbledore was planning on whatever happened at least a year in advance.
If he was in fact planning his own actual death there's no difference between that and suicide.
It would be pointless and would make no sense.

Also, if the "murder" was not a fraud, any Death Eater could have done it.
Snape need not have been involved at all and could have preserved his status as a spy.