I have a daughter that will turn 2 in July and a son that will turn 5 in June. You're tired? from one overnight every other weekend? ok....
5:45am-10am Diaper change, dress, breakfast, clean up, brush teeth. 10am - 12pm NAP TIME or QUIET TIME!!!
If nap time doesn't exist for him because I understand there are kids who would rather spend every waking moment absorbing everything they see... You provide playtime that is quiet. Old cell phone, dolls/stuffed animals, toys with sound (chicco brand or fisher price, etc), books, laundry basket full of clothes, etc.
12-2 Lunch time (prep lunch, eat, clean up) **mealtime (and bathtime) is a great opportunity to teach them words!
2-4 active playtime. park, indoor playground, mall, walk, kick/throw the ball, bubbles, shaving cream/ whipped cream (let him get messy!)