More proof that Princess Kate Middleton is on the mend: Five months after revealing she’s battling cancer, the 42-year-old was spotted with Prince William, also 42, having fun with their three kids at the Gone Wild Festival near Anmer Hall, their home in Norfolk, England.

Onlookers said the future queen playfully took part in a Nerf battle with Prince George, 11, Princess Charlotte, 9, and Prince Louis, 6. According to one news outlet, Kate “grabbed a Nerf gun, ran around, and played stuck in the mud with her kids” and was having a “wholesome family day like any other normal family.”

The royals arrived without fanfare and no photographs were taken of their fun day out. One organizer of the outdoor festival said that she was simply told a “very special VIP family” had requested to attend.

An insider exclusively tells In Touch that the outing isn’t the only time Kate — who has said she has had “good days and bad days” while undergoing chemotherapy — has gone under the radar. “Kate has been out and about increasingly more often, which is a hugely encouraging sign that she’s continuing to heal and slowly but surely getting back toward her normal schedule,” says the source. “The locals give her space, they’re very respectful and don’t pry or gossip, which is comforting for Kate and the whole family.”

Throughout her illness, the Princess of Wales has tried to keep things as normal as possible. “Not just because it lifts her own confidence,” says the source, “but it also reassures the kids that they’re going to be OK.”