It depends what you want. I've been to three of them and they all have their own character.
Tenerife we really like, despite it not being our usual sort of thing, we're going back there this summer. We like to stay in Golf del Sur, a fairly quiet place near Tenerife South airport, and I can highly recommend the villas at Sunningdale resort there, now bought out and known as the Wyndham Residences, Golf del Sur. Do get a villa , they are very reasonable, and I've just checked and they have a sale on right now till January 8th! (Book on Hotels.com and it's even cheaper, and you can save their Welcome Rewards and possibly get a bit of cashback on topcashback or quidco).
The resort is well kept and beautifully planted, and your DC would love the pool, which is very attractive, and the kids' club. Last time I was there there was entertainment round the pool on an evening, but unless you're really near the pool, nothing to scare the horses. It's quite nice to have something going on if you want to join in. The villas have a pretty planted terrace with a table, and a balcony upstairs, very nice place to sit or sunbathe.
Restaurants within easy walking distance, and a good bus service up the coast, though I would strongly recommend hiring a car and exploring the island. Los Gigantes is nice for a day trip as is the north of the island (cooler if it's warm). Also helpful for you to get to beaches, none directly there, but not too far away.
Fuerteventura is nice, but much quieter. I can recommend the Katis boutique villas at Correlejo (more pricey), though it's several years since I went. Lanzarote is quieter still, with interesting lunar type landscapes in the north. Playa Blanca is very nice, we had a lovely stay at the Jardines del Sol resort, get a bungalow or a villa there and they are very nice. Again, you really need a car to make the most of your stay.
Have a look and see what you think! 😊