Please see the invitation for house warming ceremony. Will it be better to write formal or informal invitation for this?

Please see the invitation for house warming ceremony. Will it be better to write formal or informal invitation for this? Write an informal invitation to your friend inviting her to the Golden Jubilee celebrations ofyour parent's marriage. At the House Warming Ceremony, you plan to invite your friends, relatives and colleagues. You are Raman and Shanti- Wri te out the invitation.