Malta is such an amazing place where there is no "all in one". Either "resort", or "cultural heritage", or "beautiful sandy beach". Fortunately, the island is so small that it will not take long to move from one object of interest to another (especially if you rent a car).

The best option is probably to stay in Sliema (the resort with the most convenient tourist infrastructure). From there you can reach Valletta and Floriana (a cultural heritage), then you can go to Mdina and Rabat. As for the beaches, either go to the best sandy to the west and northwest of the island, or relax on the stony in Sliema - they are also good in their own way.