May 11/12 weekend is past the spawn season (bigger fish on and around the reefs), even on a late winter season (80-90% done). Your biggest issue will be, as usual, weather. Don't change your travel dates. That time of year is usually really good, unless the weather has been bad (wind) for several days. Second half of March forecast is for cooler weather / "normal" temps. April weather can be real fickle. Unless you are targeting larger walleye (March / April), no reason to come earlier. Plus, you have a better change of getting nicer, warmer weather in May.