I have a 3 year old and 19mth old, and try to get out of the house in the morning, and then just potter around in the afternoon. I've just always done it that way.
The weeks are pretty samey samey, but everyone is happy!
Morning activities, half 9 until noon slot:
Library (just to pick books and read for a bit, or for story time)
Playgroup (I don't really feel the need to chat to other Mums, just enjoy the coffee while the children play)
Organised activity (we're doing a messy play at the moment, but previously music, gymnastics, dancing etc)
Trip to the shops/supermarket with a Babycino thrown in
Trip to indoor play centre, National Trust, museum, further afield park, just somewhere different as a 'treat'
Afternoon activities, the 2 until 5 slot:
Play dough
Glueing and sticking
Sensory tubs
Cloud dough
Baking
Cupcake decorating
Colouring
I try to have an organised activity like that each afternoon, then the rest of the time is a walk to the park, playing with toys, reading, playing in the garden, helping me around the house, then a bit of CBeebies while I make dinner.