The phrase "assemble for dinner" is correct and usable in written English.
You can use it when inviting people to gather together for a meal, typically in a social or family setting.
Example: "After a long day of activities, we will assemble for dinner at 7 PM in the dining room."
Alternatives: "gather for dinner" or "come together for dinner."
Knowing that Kate's family was assembling for dinner at her place, I called the next day for the denouement.
The local rod and gun club, joined by hundreds of friends and family, had assembled for dinner and dancing in the main ballroom of Gottscheer Hall.
The night before the dorms opened, we all assembled for dinner: Simon and Nathaniel, their mom, Frank and I. Simon had his "last" steak, before his meal plan kicked in, and eager to get on with his life as a college student, had made plans to meet a friend.
I look at people who just get up there and throw caution to the wind and do it badly, and I just cringe". Then, the long lunch completed, he stepped into the Bazaar kitchen, where the staff was already assembled, preparing for dinner.
Roughly halfway through the filming of Robert Altman's Gosford Park, word went out that the director would like the entire cast to assemble that evening for dinner - there was something he had to say.
This year, there were 28 assembled for Thanksgiving dinner.
As a tribe they all went on vacation together and assembled every night for dinner.
The Chinese couple who run this no-name restaurant were willing to let me go into the kitchen and assemble the raw materials for dinner or lunch -- noodles or rice, squash, any unknown vegetable I saw, onions, garlic, lamb or eggs or chicken.
It was not that they didn't get along; for decades the Pratts assembled for Christmas dinners, parties and clambakes, and they had a remarkable collection of estates in Glen Cove, Long Island.
