The beautiful blonde looked chic as always in a crisp white shirt and fitted jeans, which she matched with a gold belt and gold and white hi top shoes.
Heidi wore her gorgeous locks loose and sported aviator sunglasses to complete her look.
The mother-of-four was on hand to apply first aid to her sporty son Henry, who injured his nose after trying to head a football.
Heidi was quick to give her son cotton wool and encouraged him on with a big high-five. She also cheered on her nine-year-old daughter Leni and six-year-old son Johan, who looked excited to be playing in their matches.
Heidi and Martin brought snacks for the family day out, and looked happy and relaxed as they chatted to other parents. The supermodel held her three-year-old daughter Lou from the sidelines as she cheered on the rest of her sporty clan.
The couple recently celebrated their one-year anniversary earlier this month. Rumours that the lovebirds were dating first emerged in the summer of 2012 when Heidi and Martin were spotted cosying up together on holiday in Italy.
Heidi then admitted by September that the pair were an item, and was in the process of removing the tattoo of her ex-husband Seal's name.