Dad needs to file for what he wants, spelling out dates and times very clearly, including what happens if he is late to pick up for some reason. Make things as explicit as possible to prevent mom from finding loopholes. Ask for four weeks in the summer.
Dad is not going to avoid court. He needs to quit trying to bargain with mom for things that are completely reasonable and that he would get from a judge anyway. Time to cut the nonsense and just do it.

