It's a wonderful quilt! You said you don't want wiggly lines all over, but have you seen some of the designs that can be done with wavy lines and a walking foot? I will link some possibilities. Another alternative would be to do straight lines, but in a pattern -- for example, two lines 1/2" apart, then two more a couple of inches over. I will see if I can find some photo's of straight line patterns too.
https://uk.pinterest.com/explore/walking-foot-quilting/
http://betteroffthread.com/2013/03/0...ting-tutorial/
http://www.quiltingismytherapy.com/m...lting-designs/
http://www.honeybearlane.com/2011/12...-boutique.html
http://www.redpepperquilts.com/2011/...t-pattern.html