You asked about constructing a schedule. I'll share what has worked for me and the children in my life.
I generally think of the schedule as a skeleton and muscles. The bones are more firm, and tend to be things that we all need, such as meals and rest. The activites are the muscles, and I try to keep them flexible. This is what a standard day might look like.
Wake.(shower?)
Eat breakfast.
Get dressed/play. (Give this a while, kids dress slowly.)
Outside time/ physical activity. (In the summer, walking around the neighborhood in the morning is nicer than in early afternoon.)
Playtime, if any time left before-
Lunch
Art/Creative work Available: (Here I like to have paper and markers/crayons, scissors (?), dot stickers, playdough available as a bare minimum. If you are interested in adding to your art supplies, I'm happy to send you a bare-bones list.)
Reading and Rest for at least 45 minutes. NO TV. Just a pile of books (or books on tape/cd) and relaxing.
Snack.
Free play/ Wading Pool time (depending on what your family likes to do.)
Dinner.
Baths, stories, bedtime.
I've found over the years that the more rigid the schedule, the more impossible it is to keep. That said, I usually decide on one or two things that I really want to do and focus on those, keeping the meals and rest in mind, but letting go of other expectations. A rigid schedule is misery for everyone, so stay flexible!
Just a suggestion, but parks are free and can be endlessly fun for everyone. You can pack up a picnic the night before
and spend the entire morning out somewhere. Playdates will also keep your older one busy with a friend, and you might find that having a chance to trade care will give yourself and your youngest a little freedom to do some things that you enjoy which might be easier to do with one child!