it depends on your personal parenting philosophies.
I like the AP/gentle approach of giving your baby what it needs, or medically backed up evidnce/research - not just what i think is the most convienient to me:P
would you let him cry to sleep? is that how your MIL gets him to sleep?? do you both have similar ideas?

personally, i feed to sleep, bree is now 20 months and i am happy to still do so, but i know she can go to sleep without it if she had too, but i'd expect my mum to rock her to sleep if she needed it and not let her cry