To change all the verbs to active voice in the paragraph, the following option is correct:
Eliza and Elliot loved the backyard playhouse that their dad, Ted, built. Eliza and Elliot gave Ted input to design the house. Ted built the house with plywood and nails. Eliza won the coin toss, so Ted painted the outside of the house pink once he had finished building its structure. Once Ted finished the outside, Eliza and Elliot decorated the inside.
This choice changes the verbs to active voice by specifying the subjects performing the actions.