Marbella Spain or Vilamoura Portugal?

My only consideration would be the ease of getting to one or the other. Without a rental car, getting to the Portugal destination might be more complicated.

Thank you for the response @jaimeelsabio. We will have a car all summer and have reserved parking at both destinations.

You might get varying responses see here. The Algarve is great for a beach holiday (except the sea is very cold!) but Vilamoura is a purpose built resort and not the most atmospheric location. Carvoeiro is a really nice resort town for families with restaurants and a good buzz in summer.

Marbella is busy and a maybe a little bit brash. I don’t think the beach is anything amazing either. Some of the Algarve beaches are absolutely gorgeous and with a car you can easily explore. They always have really nice beach restaurants too. I love Portugal!

Several years ago, I spend 3-4 days in Costa del Sol area of Spain and was not at all impressed with the beaches. I grew up on coastal Georgia near beaches and frankly wouldn't advise spending a euro on going there to go to the beach.

Marbella is a very nice area but expensive. Another reason to do something else.

Thank you @Helen and @geovagriffith for your helpful commentary! It's been a bear to think through this not knowing the areas and really appreciate the feedback!

Have you come across the Martinhal resorts in Sagres and Quint da Lago during your searches? I haven’t been to either but know a number of people who have and really like them. They’re upmarket but kind of low key resorts aimed at families with young children.

Marbella has a small, pleasant old town that is nice to wander around and there's a 9th century castle right in the middle. The surrounding newer town is also pleasant with lots of tree lined avenues and pedestrianised areas. The beaches aren't amazing but they're sandy beaches with plenty of infrastructure and a variety of bars, restaurants and cafes in the vicinity and perfect for young children. Marbella isn't expensive, it's no more expensive than anywhere else along the Costa Del Sol. I've been taking my kids there since they were toddlers (they're now in their late teens) so I've got a good experience of prices. It's more upmarket than some of the other nearby towns such as Benalmadena or Fuengirola and there are plenty of Michelin starred restaurants and expensive boutiques however there are equally many more reasonably priced restaurants and shops.

You're also within easy driving distance of Malaga where I'm sure the kids would love exploring the Alcazaba and the music museum is fantastic, touching is very much encouraged and the kids can bang, strum, pluck all the instruments to their hearts content (adults also enjoy it too!).

Nerja offers the caves which the kids would undoubtedly enjoy whilst in the other direction there's nearby Estepona whcih has a nicer beach than Marbella and a lovely old town that still retains much of its unspoilt charm which is in contrast to much of the overbuilt Costa Del Sol.

There are aquaparks aplenty all along the coast and if you're tired of the water then head inland up into the mountains and explore the many towns and villages dotted throughout.

I haven't been to Vilamoura or the Algarve in general but I think you'll find more to see and do basing yourself in Marbella.