I used to agree with your mom, but now I love sewing on knits! What kind of machine do you have? Does it have a setting for knits? Make sure that you use it!! ;) Or use a wonky stitch, the zig- zag stitch, that looks almost straight. Mc Calls and Simplicity both have darling patterns just for knits for children. Look at the stretch requirement on the side. Put in a brand new needle, for knits or stretch fabric. Be careful cutting your pattern, use pins for knit fabric. Once you get the hang of it, you will love sewing with stretchy fabric.
You can PM me if I can be of more help. :?