Little Ollie Hall wanted to do something to help after learning about coronavirus from his parents.
The prime minister's pregnant fiancée also praised the "magnificent" NHS in a Twitter post.
A string of luxury labels around the world are turning over their factories for the fight against the pandemic.
"It’s a nod of appreciation to the people who work tirelessly day in, day out to keep us safe and healthy."
The Duke of Cambridge passed on the thanks of his grandmother and father during the visit in Croydon.
Entertainment professionals have offered their skills to assist the NHS in increasing care capacity during the coronavirus pandemic.