Those hearts were hand appliqud, although machine applique would work too.
In every quilt, I put in the amount of time the quilt seems to require. I have hand appliqued several charity quilts. You need to do what is comfortable for you. I try to make every charity quilt be good looking and good work, regardless of how much work there is. I try for fabrics that make it interesting both for me and for the person who gets it.
I have posted a pieced heart quilt I did, which was one of my earliest quilt designs. I don't find a picture of an early charity quilt that I did which was a large walking, fleece machine appliqued teddy bear holding 3 heart shaped balloons on strings. Feel free to do what works for you.