Carter is best known as Downton Abbey’s Mr Carson. Staunton was Oscar nominated for her role in Vera Drake.
Both actors have been patrons of Greenfingers since early 2014.
The event saw a group of diners join the actors to raise pledges of support for the work Greenfingers do in supporting children and families in children’s hospices around the UK.
Carter said: "What a fantastic evening! It is wonderful to be here in such delightful surroundings, eating such delicious food, in wonderful company and bringing together people to hear about Greenfingers, a charity that means a lot to us, and the work they do for children who spend time in hospices around the country, offering them vibrant and exciting outdoor spaces for them to relax in and enjoy."