Everything you planned seems wonderful. Take them out side bug exploring and fossil hunting in the morning before it gets too hot. Give them each a little bucket or bag to put things they find interesting in (flowers, rocks, etc). Bring a snack and some water and have a little snack break outside.
Come back to the house and cool off - rest a little. Watch TV for @ 30 minutes.
Eat lunch and decorate cookies for dessert.
Afternoon - paint with water - get cheap foam brushes and water and let the kids make pictures with water on the sidewalk or side of your house. Also, sidewalk chalk. OR wash toys - get a bucket of soapy water and sponges and let the kids wash toys outside. Its messy and fun. Finally - play in the sprinkler or get out the kiddie pool.
Inside craft - glue pictures. Get dried beans, rice, pasta, ripped up pieces of paper, etc and give kids glue and coloring book pictures. They can either outline the picture with glue and beans, or fill in the inside and glue different items on.
Watch some more tv. Be careful planning too many activities that require you to direct the kids and them to all do the exact same thing at the same time.
Have fun!