Much, much more quilting information….
I am making the assumption that either you are a quilter and know how to make a quilt OR you have access to a quilter/class who can guide you through the process. So what I have written below is not an exhaustive quilting guide, just some notes to make sure we are on the same page technically. The most important part of your Piecing Hope Quilt is the fabric you use to piece the top and the fabric used as the backing!
Quilt fabric
Here's a simple test to see if your fabric is suitable: Close your eyes and feel it. Is it coarse or rough feeling? Is the weave loose? Can you see through it? Does it feel "hard" or scratchy and not soft to the touch? If you answered 'yes' to any of these answers, the fabric is absolutely NOT suitable for a Piecing Hope Quilt.

Think of it this way... in simple terms, would you want a child to have coarse, hard or scratchy fabric near his or her skin? Your Piecing Hope quilt is being made to provide comfort, love and hope. Think of what you would want to snuggle up with - a quilt that's soft? Absolutely! And that is why you are asked to use good quality 100% cotton fabric. Your quilt is being made for a child of God. Don't they deserve the good quality fabric?
For any quilt, it all starts with the fabric. If the fabric is not good quality, no matter how pretty it is, how well you piece it, how well it is quilted or how great your label is, it will not last through the years or survive multiple washings. Not only does your Piecing Hope quilt provide comfort today - it should be made to last for many years in the future.
All fabric should be washed before you cut and piece it. The backing fabric should also be washed before you send your top to a longarmer or begin quilting it yourself.
Lastly, a mention about the thread you use to piece your top. Good quality 100% soft cotton thread is the best. Use machine quilt thread rather than the stiffer hand quilting thread. The weight of your thread should be 50. Do not use machine embroidery thread (40 weight rayon or polyester) to piece your top. It will not hold up in the long run.
Backing fabric
Wide backing fabrics are often less expensive than buying enough fabric to piece the backing.
I think we all get price shock when we go to purchase the backing for our quilts. So don't be tempted to scrimp here.
Instead arrange to go and speak in your community to drum up financial help. It's important that you tell them exactly what you need. Don't do a "whatever". There's nothing worse than to have your donors try and guess what your needs are.
There are some great 100% cotton quilt backing fabrics which do not require piecing. Look on-line and at your local quilt store. Flannel is lovely but make sure it's well made. Cheap flannel pills easily and then feels like sandpaper. Muslin? Don't go there. There are plenty of excellent quality cotton fabrics that you can use that are hundreds of times better than muslin. To me, muslin says "cheap" and "you're not really worth the expensive stuff".
Remember when you are putting your backing together, you have to think 3 - 4 inches extending from all sides of your top. If you have to sew a seam somewhere on the back, make sure the selvages are off (unless it's on the outer edge). Selvages don't give and increase the likelihood of puckering. Be sure to ask your longarmer if they want the sewn seams pressed open or to the side.