Hi Abigail, I use safflower, sunflower or canola
oil to substitute for butter and margarine all the
time.  Use the same proportion as solid fat.
Comes out great and it's healthier too!.  I watch
my fat intake, so what I do is:  add 1/2 the amt
of oil and 1/2 substitute apple sauce or pears
blended up fine from blender.  Works well for
adults.  Rosalie in NJ