If it were me, I'd do it this way:(given your mother's constraints, mind you)
Have breakfast.
Stay outside for as long as possible.
Come in, morning snack.
Storytime/playtime.
Nap
Lunch(12:30ish--1ish)
Open-ended playtime. (mom should not be doing every little thing with the wee one. She can bring out the blocks or set up the playdough, etc. and get him started, or work side-by-side with him if she likes.)
Storytime.
Snacktime (I would do it around 3ish, something not too heavy)
Bathtime/water play time
Playtime
Dinner/mom home, etc.
Evening routine.
At this age, the best 'educational' toys are the ones that provide the most open-ended play possibilities. Blocks, playdough, a few cars and cardboard ramps.... Sometimes, kids need something new, so don't offer everything at once. Water play can sometimes be scoops, sometimes lids (attach an adhesive magnet on the end of a craft stick-- loads of fun for the kids to 'fish'), sometimes sink/float items or sponges. Play dishes can be washed in cool, soapy water. (If you don't have a tub, you can use a big pot of water on the floor-- put a couple towels under it to prevent slip/fall accidents).
Clear contact paper is great for making 'collages' of torn paper and random items you could find everyday-- twist ties and bread tabs, cut up mesh bagging from veggies.... or go to the craft store and get some $1 bags of sequins. Cut up yarn or old scraps of cloth-- it's just for fun.
Big crayons are fun at this age. Offer thicker paper for this-- even recycled cereal boxes are great.
"Painting"-- offer some paintbrushes and water-- let your son paint construction paper with this simple set. (It gets dark.) Offer larger river rocks as well.
Offer a bigger box for him to climb into. Cut a hole in one side so he can peek out. Let him make of it what he will...
There are a few good books on activities for this age, PM me if you want a list. Many toddlers LOVE sensory activities. And if your mom is physical- let her watch a workout video and see if your little guy will try to do some of the moves he's watching grandma do.