Electrician

I have a 200amp main and would like to put a sub panel 100amp off of it (their is a 2 pole breaker 60 amp in it) it feeds a/c and water pump iwould like to change 60 breaker to 100 and feed sub then put in 2 double pole breaker for a/c and water but i also have to run a line off of sub to another sub panel by the dock to feed 2 circuits light s and motor lift (running quad plex #2 to sub by dock 250ft run 220 to dock panel split 2 20 amp circuits can this be done how do i hook up the #2 to 1st sub panel and then to sub panel at dock