Is Dumbledore's request of the Dursleys Reasonable (Spoilers for HBP)

[christopher]

No: HPFGUIDX 133432

This is my first post, so I hope it is put together okay.  Anyway in 
Chapter 3 (Will and Won't) of HBP, after explaining about the blood 
protection (Voldermort cannot hurt Harry whilst he is at the 
Dursleys'), Dumbledore asks the Dursleys to let Harry return one more 
time, so that the protection lasts until he is seventeen.

This seems reasnoable on the surface, but imo it is not reasonable.

Here is my reasoning.

1:  We know the protection applies to Harry, but does it protect the 
Dursley's as well.

2:  If it doesn't protect the Dursley's then Dumbledore is asking them 
to risk their lives for a world, which they don't want to be involved 
in.

Voldermort from what i understand, is quite capble of killing or 
ordering killing to be done.

Christopher