Chris,
I would bet that the crappie and bluegill are not necessarily “late to the party”. One can find panfish in shallow water one day and deep the next in the spring, timing is everything. This pattern seems to hold pretty solid until spawn. I think in general most folks have the best luck fishing sharp breaks or transition zones where multiple depths can be found in a short distance. A good example is I spoke with a “walleye guide” who found crappie in 30’+ at Sherman a week or so go and that same day I found and caught crappie in 9’ to 35’. I never under estimate crappie this time of year.
"Indeed, the single biggest reason we're not catching fish spring, summer, winter, or fall is that there are no fish where we're fishing."
Gord Pyzer