Should work fine. Are they synthetic fill or down? (synthetic pretty much means you can go after it with abandon- the down means you'd have to be a bit careful to avoid a down blizzard)
How heavy are they? You might be able to cut them both up for quilts to save a bit of weight.
But bottom line: will work.
(For our american etc friends, I think kiwi is talking about Centigrade ratings, not Farenheit.
0-5 C is 31-42 F. )