Not really on 1 flight. JAL usually releases 4 award seats in each cabin initially and usually a few more later but only 1-2 day prior to departure. So the chance of getting 8 J award seats on one flight is quite slim. However, there seems to be 2 flight each day from MNL to NRT each day about 4 hours apart, so you may want to separate your family into two groups to issue award tickets.