Good thinking! As you've granted land to the families, they now owe you allegiance. Norman knights are noted for their skills in warfare. Your army will benefit from this.
Placing trust in the nobles will gain you popularity with them. They will exert authority in the region as sheriffs on your behalf. But be careful, they cannot be everywhere. Concentrate on the south-west first of all.
Well done. New Anglo-Norman settlers have pledged military support and their allegiance to you as ruler. They are building motte-and-bailey castles. It is the beginning of the castle-building era in Scotland. Things are starting to look up!