I was staying in the area last Easter (31st March for 2 weeks) and we toured the Royal Wings (stayed there in October). The waterpark was open for a couple of hours morning and afternoon when weather permitted (we had great weather with 1 day of rain) but the pools were freezing. I think if demand is there and enough people ask they will open it. Obviously this would depend on their staffing levels also, so the official line is 'no', but you may find it is - not that helpful I know but hope that helps a little. I would suggest emailing the hotel, but my experience is they are not great at replying! A fantastic hotel though - we loved it!