Doug McLeod (David Tennant) and his wife Abi (Rosamund Pike) unite following a tense separation to travel to the Scottish Highlands for Doug's father Gordie's (Billy Connolly) birthday. Gordie has terminal cancer so Doug's brother, millionaire Gavin McLeod (Ben Miller) has arranged a lavish party for him, inviting all important people in the neighbourhood. Despite difficulties getting their three children, Lottie (Emilia Jones), Mickey (Bobby Smalldridge) and Jess (Harriet Turnbull), to leave the house, they hit the road, but find it congested and they are forced to stop overnight. Lottie expresses her troubles with trusting her parents following their recent separation and lies to each other; it is revealed that Doug had an affair, which lead to Abi moving out and taking legal proceedings against him. They are only travelling to the Highlands together to appear as a couple before Gordie, not wanting to upset him in his current health situation.
On arriving at Gavin's mansion, a tense rivalry becomes apparent between Doug and Gavin, while Gordie, despite being extremely ill, is fun-loving and encourages the children, particularly Lottie, to let go of their troubles and enjoy life. While Gavin, Doug, Abi and Gavin's wife Margaret (Amelia Bullmore) make the final arrangements for the party, Gordie takes the three children to the beach. He reveals that he is descended from Vikings, a fact that Mickey in particular is excited about; he reveals his desire to die 'the Viking way' and be cremated and sent out to sea. He believes this will stop arguments between Doug and Gavin. Later, while Lottie, Mickey and Jess are playing, Gordie dies, and due to having no phone signal Lottie runs back to the house to tell the adults, leaving Mickey and Jess with Gordie's body. However, when she sees them all arguing, Doug with Abi about plans for them to move to Newcastle, and Gavin with his family over what Gordie wants for his birthday, she returns without telling them. Fulfilling Gordie's last wish, the three children create a raft, and, using petrol from Gordie's pickup, send him out to sea aflame.
They return home, and tell a horrified Doug and Abi what has happened. Doug and Gavin head to the beach, where they spot the raft aflame far out to sea; Gavin breaks down in Doug's arms over what has happened. Abi and Margaret break the news that Gordie has died to the horrified party guests, and the police, accompanied by nosy social services worker Agnes Chisholm (Celia Imrie), who interviews the children on their actions, contemplating removing them from them from Doug and Abi's care. The press descend on the house, with Lottie, Jess and Mickey's actions headline news worldwide, and Margaret's previous actions in attacking a fellow shopper at a supermarket while experiencing depression is revealed when Mickey and Jess accidentally stumble upon it on Gavin and Margaret's son Kenneth's (Lewis Davie) computer. Gavin struggles with this but ultimately moves on. Doug and Abi make a statement to the press stating that they have the other's full agreement that they are both competent parents; as a result, Chisholm ends her investigation.
Several weeks later, when the press storm has died down, Gavin and Doug hold a memorial for Gordie at the beach, where the brothers support each other and are shown to have buried the hatchet. Abi also reveals she has decided not to move to Newcastle, and the couple begin working out their problems as a family unit, last seen having fun on the beach as a five.
After watching What We Did On Our Holiday last night I got to thinking how much like the eldest child, Lottie, I was as a child and I still am in some ways.
I am thinking in terms of her concerns about getting it right and her ability to see the inconsistency in her parents and most adults she has contact with, except her beloved grand-father. For me it was my father. How she is so concerned about getting it wrong that she feels the need to write everything down, just incase she forgets something or gets it wrong.
Life can be like that. It can throw us so many confusions and anomalies that we can't keep up with it and feel that the only way to understand it all, and keep yourself innocent, is to log it, either in your note book, as Lottie did, or in your mind / body, which is what I think I have done.
The life and place that Lottie had in the family made me cry. For me, she was the main character and the one that showed me the truth of my experiences. Her story, hit me hard. And I left the cinema determined to start afresh, to throw my notebook away, so to speak. But this has proved much harder that Lottie made it seem. I am struggling daily to 'let go' of everything that has been written in my cells, subconscious, and wherever else it is written.
That said, I am improving and I am also being less in my head and more in the 'now'.