I find the playground quite difficult with two -- running in different directions. Good for you for managing it!! I need some helpful hints on that one.
Some of my ideas sound either boring or elaborate but the age group you have is fantastic for simple easy fun. Small things can be made into a big deal. Like "tomorrow is picnic day" and even if there is nothing more special about it then eating on the floor on a blanket, those girls might think its the best thing ever. Something to look forward to, and fun.
Coloring -- not just crayons but those markers that only work on certain paper
Chalk drawing
Dance parties (I do tea party with my daughter but the 1 year old can't sit still so we turn it into a dance party too -- simple hair ribbons could really make them very eager without a lot of investment/mess)
Blocks
Picnic outside or inside -- extends meal time
Nature crafts -- go out and collect different leaves or grass or flowers, can glue them when the younger one sleeps or just collect them
I will be back to think of more... for now I'm so sleepy my brain isn't working. But keep the simple thing in mind, sometimes just someone saying "tomorrow we're going to go for a walk" is enough to keep them smiling and looking forward to a new adventure.