I'm from hull and are going to scarborough, whitby, york then back to hull over easter, camping.
try going to bridlington (day 1) 30 miles, york (day 2) - 40 miles, back to hull day 3 40 miles
plenty of campsites around all.
if that is too much
hull to withernsea (day 1) 20 miles, withersea to bridlington day 2, back to hull day 3
all fairly flat