I live in that area, but sadly most of my experience is places without concrete pads.
The state parks have pads for the handicapped spots, but otherwise not... several good choices though....
Hanna park is a city owned place....all full hook-up but not many with concrete pads, very surprising topography though for this area...sites scattered throughout nice foliage and hilly terrain, what used to be sand dunes now wooded with nice bike trails. Maybe a bit more rustic than you're looking for though....
Feb can be very pleasant here...but it can also get quite cold some years. yeah, yeah...not Michigan cold...but whatever. it's damp bone chilling cold.
My advise is keep plans soft and be prepared to head a bit further south
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