I think once you get it on the frame it should be fine with a puffy batting. You would be surprised how much the batting will take care of the puffyness..

For the one and only top your MIL every made, it was a lot of work, and she did a very decent job. And if it is 30 years old, they sure didn't have all the lovely rulers and cutting tools we have. If there are areas that are seriously out of whack, I would measure the block. Maybe a small adjustment in the seam would help. As to the quilting--quilt it with love--that's all that really matters in the end.

I wonder if she used poly/cotton and cotton mixed? Sometimes you will get puckering that way, or if the iron is too hot.

I am sure she will never notice as long as its finished.

This will be like so many of the other "wonky and wobbely" projects. When it is quilted, it will be lovely and nobody will notice the wonkers and wobblers.

The stars lend themselves to be quilted 1/4" in from the seam. You could do a braid down the pink center with a round-is pattern in the 9-patch. You can start basic and add to it once the basics are in place.

Use a polyester batt ... they are more forgiving to problems and can help camouflage them well. The higher loft the better ... that is, so long as you don't mind the poofy look! If you do, just use the regular poly.

For a one and only she sure did a good job- look at those points! My first quilt had all the points chopped off :D
I like Mad Quilter's ideas a lot.

I can't believe how perfect those points are! Your MIL should take up quilting again. I agree with the others that it doesn't look wonky in the photos, and a thickish batt will take care of any problems. I think it will be a lovely quilt when it's finished, and it's a sign of her confidence in you that she has asked you to quilt it.

She will like it no matter how it turns out. Like other's said use thick poly batting after quilting wash and dry it will be fine.
If some blocks are really bad... you could rip a little and re sew a little.

This is one thing I like so much about this board. Everyone is so gracious, for the most part, and that means so much.