I do not like to make continuous bias binding (the technique where you sew the fabric into a circle first) because it ends up with so many seams in it. When I make bias binding, I just cut straight strips the same way I always do (with a June Taylor shape cutter mat) except that the fabric is folded along the bias instead of the straight-of-grain.
Are the edges of your quilt already cut into scallops? It is more common to leave the edges of a quilt straight, mark the scallops, then sew your bias binding to the quilt following the lines. This is easier than trying to sew to a cut edge. Here is a tutorial that shows this (there are more if you Google, including Youtube videos:
http://www.ludlowquiltandsew.co.uk/a...quilt-binding/
Are you sure that 5" wide strips will work on your scallops? If you have not done scallops before, I would definitely experiment with a sample quilt and bias fabric cut 5" wide to make sure your idea will work. Scallops are normally bound with thin strips of bias -- about 1.5" wide -- because the inside corners are so difficult. I don't believe I have ever seen wide binding on a scalloped edge. It is the scallops that vary in size -- the binding, not so much.
My guess is that a yard of fabric would probably be enough to bind a lap size quilt with scallops if the bias strips are cut a normal width (about 1.5"). I don't think a yard of fabric would be enough for a lap size quilt if the binding strips are cut 5" wide. What you need to do is take a tape measure to your quilt and measure around the edge; that will at least give you a starting estimate of the length of binding you will need (you will still need to add some inches for security).
I think the only way you are going to know if 5" binding strips will work is to try it out on a test quilt sandwich first. A lot depends on the size of your scallops. My best guess is that 5"-wide bias binding strips might work if the scallops are large and shallow; I'm thinking small and deep scallops require narrower binding.