Go for it. I agree I would just check the weave of the fabric to make sure that the fabric doesn't unravel for the narrow seam allowance.
I don't think there is enough difference in the shrinking but it will depend on how densly it is quilted on how it ends up looking. Densly quilted no problem as the one fabric that doesn't shrink will tend to stabalize the other.
I use sheets often too but make sure they are durable first.