For his appetite, are you worried he's not eating enough throughout the day/night? If so, then yes, you want to see him eat with his shot time to make sure he doesn't drop too fast. But, if he's eating enough, with Lantus it's more important to eat around nadir/+5-7 hours after shot time than it is to eat at actual shot time.
For me, once I figured out how much on average Michelangelo needed to eat each day, I no longer worried about him eating at shot time. Both of my boys (8 months and 1 year and a month old) eat about 2 cans of Friskies one day and 5 cans the next and other variations. It all equals out to about 4 cans a day over the span of a week. So as long as I see him consuming "enough," I'm not too worried if his appetite fluctuates from day to day.