Dear (Put the recipient’s name)
I hope my letter finds you in the pink of your health. How are Robert and Madeline doing? (Start by talking about the person to whom you are writing, ask about his/her health, family and general questions).
I am writing to let you know that I will be coming to Florida for an official conference and hope to be free this weekend. It’s been ages since we saw each other and it will be a good idea to catch up on old times. (Give main reason for writing letter, if any. This is the longest part of the letter, so you can fill in other details too.)
Please let me know if you are free and we can take the kids along too, just like the old times. (Wrap up the letter in this paragraph; mention any more plans if needed). Looking forward to seeing you,