If you want to fly from Edinburgh, you could do a lot worse than look at Jet2holidays.
Package holidays are just a way of booking accommodation, flights and transfers all in one go and aren't limited to beach/pool holidays in AI resorts miles from anywhere. They could look exactly the same as something you book yourself but you have more help/protection if things go wrong. They can be cheaper or more expensive than booking separately, I've seen it go either way.
On the Jet2 website, you can enter your dates, party size, locations you are interested in and then filter by board type, Trip Advisor rating etc and sort by price.
I like B&B but with at least a fridge and ideally a kitchenette in the room then you can mix and match with eating out for lunch or dinner and keep drinks, snacks, ice creams etc plus bread, cheese, olives etc from the supermarket in the room. I don't like AI unless it's a la carte and that is very expensive. A decent sized balcony or terrace is also a must as we always sit outside any time we are in the accommodation. We generally never use the inside living area except for sleeping, washing and food preparation.
Then use Google maps to check the location - we always want to be in walking distance from the beach, restaurants and at least a decent sized convenience store.
Anywhere like the Canaries, Greek Islands, Cyprus, Malta, Spanish Costas, Balearics, Croatia is likely to have watersports available locally (scuba diving, paddle boarding, coasteering etc) plus maybe museums, hiking, mountain biking, ancient ruins, castles, waterparks, Lanzarote has a volcano park, on Tenerife you can take the cable car to the top of Mount Teide (be prepared, it is bloody freezing, even on hot days).
Plus you mention Valencia, many Spanish Costas are close to cities where you can also have the city break experience (Barcelona, Alicante, Malaga, Palma).