Christina Aguilera and son Max
01/13/2012 at 04:00 PM EST
had a big date on Thursday with her son, Max.
The singer, along with boyfriend Matt Rutler
, headed to California's Legoland to celebrate Max's fourth birthday
. The threesome, along with about 16 others, spent around five hours at the amusement park, and enjoyed time in Miniland Las Vegas and Hideaways. They also rode Treasure Falls and Lost Kingdom Adventure, and Max drove a car in Volvo Junior Driving School, an onlooker tells PEOPLE.
The singer shared her fond memories after the trip: "Spent today at Legoland with the love of my life. Happy bday Max!" Aguilera Tweeted
To top off the day, Legoland created a vanilla cake with vanilla frosting and LEGO brick décor on it for Max. The birthday boy also got a birthday button when he got there – and he wore it the entire time. – Mia McNiece and Sara Hammel