I'll leave others to replies re cultural things to do as we only go to Benidorm for rest and relaxation. Gone are the days when I had to see everything of interest there was to see.
However we are going to try and see Parque Elche (Dove Park) when we go back. It was closed for refurbishment last time we were there. Sanji has a video of it in the Video Gallery at the top of the forum.
There are plenty acts to keep you going for a few days or more along Calle Gerona. You will find recommendations in the Bars and Acts topic at the top of the forum. The ones we have enjoyed have been Westlife at Morgan Tavern, Peatloaf at various places including Stardust, Abbaesque are passable, but I wouldn't go out of my way to see them. Tony Scott the comedian was quite good, but Albi Senior was just OK. The Beagles at Jail Rock are pleasant to listen to, but it's exactly the same set every night. The Western Saloon sometimes has good acts if you like Country music. Can't remember where we saw the Bay City Rollers, but we really enjoyed watching them.
We found Rocker Fellas to be the dearest for drinks at about €11 for 2, but you pay a premium in all the bars with entertainment.
We had a couple of good meals at Two Palms on Calle Palma in the Old Town and an excellent night in their Music Hall bar across the road where we met Howard Kendall, ex Everton manager.
Do you know where you are staying yet as you can check the reviews and see what other members thought of it?
Hope you have a great time and look forward to a trip report on your return.
luci