Here's a suggestive itinerary for a 3-night holiday at PortAventura from the UK:

Day 1: Arrival in PortAventura

• Fly from the UK to Barcelona or Reus Airport, which are both close to PortAventura.
• Arrive at your hotel in PortAventura and check-in.
• Spend the afternoon exploring the resort and familiarizing yourself with the various attractions and entertainment options.
• Enjoy dinner at one of the resort's restaurants.

Day 2: PortAventura Park

• Start your day at PortAventura Park, the main theme park of the resort.
• Experience thrilling rides and roller coasters like Shambhala and Dragon Khan.
• Explore themed areas such as Mediterrània, Polynesia, China, Mexico, and Far West.
• Enjoy live shows and entertainment throughout the day.
• Indulge in a variety of dining options within the park.
• In the evening, watch the spectacular fireworks display.

Day 3: Costa Caribe Aquatic Park

• Spend the day at Costa Caribe Aquatic Park, the water park within the PortAventura resort.
• Enjoy a range of water slides, lazy rivers, wave pools, and play areas.
• Relax in sun loungers and enjoy the tropical atmosphere.
• Treat yourself to refreshing drinks and snacks from the park's dining options.
• In the evening, you can explore the resort's entertainment offerings, such as evening shows or live music.

Day 4: Free Day and Explore the Surroundings

• Use this day to relax and enjoy the amenities of your hotel or explore the surrounding area.
• Take a day trip to the nearby city of Tarragona, known for its Roman ruins and historic sites.
• Explore the beautiful beaches of the Costa Dorada and soak up the sun.
• Visit nearby attractions like Ferrari Land, a theme park dedicated to the famous car brand (located within PortAventura Resort), or the Aquopolis water park in La Pineda.
• In the evening, enjoy a final dinner at one of the resort's restaurants or venture out to try local cuisine.

Day 5: Departure

• Enjoy your final breakfast at the hotel.
• Check out and transfer to the airport for your return flight to the UK.

Please note that this itinerary is a general suggestion for a 3-night holiday at PortAventura, and you can adjust it based on your preferences and the specific attractions and activities you wish to experience. PortAventura offers a wide range of thrilling rides, water attractions, entertainment shows, and dining options to cater to all ages and interests.