S.S.
I would totally skip the pool and sprinkler. It will be a huge mess. Now having said that if you are having toddlers maybe you could set up a potty chair station somewhere outside. maybe inside a little tent or use some sheets and make a little "restroom" for the toddlers. probably more hassle than you want but if it was me I would skip the water mess altogether lol. good luck hope you have a fun party.
I had a huge 50th party for my husband a couple weeks ago. there were about 70 people and a good 20 of them were under the age of 8. we set up a shade tent thing and put a table and chairs under it. I taped down a long drawing sheet (got it at hobby lobby) on both sides of a banquet table and put crayons, colored pencils and markers in the middle of the table on the driveway we put orange cones so no one tried to park in the drive. we put out colored chalk, bubbles and a horse shoe game and a ring toss (both from party city clearance bin) it kept the kids entertained without making a big mess.