New to this and arriving tomorrow night for our first disneyland trip! planning 1 day at universal (family of 4, 2 girls ages 8&10). My question: we arrive late sunday night, I don’t think we can rope drop a park monday morning. Planning to get 3 day park hoppers. for the 3rd day, should we use this to go to the parks Monday afternoon/evening or should we use it to go friday morning until approximately 2pm (our flight leaves at 5pm)?
also - is there a touring plan that incorporates using park hoppers rather than 1 park at a time? thanks!
There are no plans that incorporate park hoppers, you have to make one for each park for whatever part of the day you plan to be there. If you do not go to a park on Monday, what will you do otherwise? If you don’t really have other plans, I would get 4 day hoppers and go both days. 
Crowds will be less on Friday morning than on Monday afternoon/evening, but you will likely be more tired on Friday morning so you might want to sleep in before the end of your trip. It’s really personal preference.