I would do AK Sunday rather than Monday as Easter Sunday tends to be its "light" day (still very crowded but not as bad as during the week). Do not make any decisions based on an assumption that weekends are more crowded at places because local residents come; local residents avoid WDW like the plague during Easter time. MK will be packed everyday with Easter Sunday its worst (which helps the other parks) followed by Monday.When whether is warm during that time, waterparks tend to fill to capacity by 11:00 to 12 every day and which day you choose makes no difference (and if you want any chance of getting decent chairs somewhere you best get there early). As to using early entry at a park, the first thing you want to do when you get there is ask for early entry schedule -- sometimes, not every year, they simply open all the parks an hour or more early everyday and do not decide to do so until just before doing it. If they are not doing that, then early entry should otherwise be used if you can as that may be one of your few opportunities to get on some attractions without huge lines (and you can get sustained lines of 2 hours or more for the more popular attractions after 10:30) -- just consider switching to somewhere else by 11 or so because that park becomes monstrously crowded after then. Use fast pass when you can but be aware that for some popular rides all the fast passes for the day can be gone by noon.
