She and her husband have 1 slice each and her children split 1 slice so that's 1+1+.5+.5 = <<1+1+.5+.5=3>>3 slices
She makes 3 pieces of french toast on Saturday and Sunday for a total of 3*2 = <<3*2=6>>6 slices per weekend
If she uses 6 slices per weekend then over 52 weeks she will have used 6*52 = <<6*52=312>>312 slices
She gets 12 slices per loaf and she needs 312 slices so she needs 312/12 = <<312/12=26>>26 loaves
#### 26