M.M.
If you insist on cooking for your grown children (who should be fending for themselves, by the way), then you need to make them work around when you're cooking.
1 breakfast, 1 lunch, 1 dinner.
If they are hungry around that, they're on their own.
Sounds like breakfast and lunch should be planned around your son, since he is most consistent - and the rest of the family can eat leftovers from that when they get up or are ready. Then dinner when everyone is home.
Again, no chance would I be cooking all this for these kids everyday. They're grown. Let THEM cook for YOU for a change! I'm exhausted reading this!