There is a well-known Halachic principle "En Kiddush Ela Bi’mkom Se’uda," which requires reciting Kiddush on Shabbat (or Yom Tob) in the same place where one’s meal will then be eaten. The question arises as to whether this Halacha pertains only to location, or also to time. Meaning, does this Halacha require reciting Kiddush in the place where the meal will be eaten and also right before the meal begins, or does it require only that the meal be eaten in that location, even if it begins a long time after the recitation of Kiddush?
The Rama (Rav Moshe Isserles of Cracow, 1530-1572) writes (273), "Ve’sarich Le’echol Bi’mkom Kiddush Le’altar" – "One must eat in the place where Kiddush [was recited], immediately." The Mishna Berura (Rav Yisrael Meir Kagan, 1839-1933) explains, "One should not interrupt, even for a short time." From the comments of the Rama and Mishna Berura it appears that one must endeavor to begin his meal – whether he’s eating "Mezonot" food," or bread – immediately after the recitation of Kiddush, as soon as possible.
A more lenient position emerges from the discussion of the Aruch Ha’shulhan (Rav Yechiel Michel Epstein of Nevarduk, 1829-1908). He writes (273:4; listen to audio recording for precise citation) that when the Rama requires beginning the meal "Le’altar" ("immediately"), he does mean this literally, that one must immediately proceed to the meal without any delay whatsoever. He draws proof from the case discussed in the Halachic sources of one who recites Kiddush on one floor and then eats his meal on the second floor, upstairs. Quite obviously, a few moments – at least – are needed to reach the second floor, and yet even this qualifies as "Kiddush Bi’mkom Se’uda." Accordingly, the Aruch Ha’shulhan contends that the Rama’s intent is merely that one should not excessively delay beginning the meal after Kiddush. Certainly, he writes, it is acceptable to change into one’s slippers or put on one’s robe after Kiddush before beginning the meal. The Aruch Ha’shulhan applies to this Halacha the famous Halachic axiom, "Lo Nitena Torah Le’mal’acheh Ha’sharet" – "The Torah was not given to the ministering angels." Meaning, we are only human, and so we cannot be expected to begin our meal immediately after Kiddush, without any delay at all. Therefore, it is acceptable to begin the meal a few minutes after Kiddush.
Other Halachic authorities specify the time-period of "Kedeh Achilat Paress" – the time-frame within which a Ke’zayit of bread must be eaten in order for Birkat Ha’mazon to be required. However, there are many different views as to what "Kedeh Achilat Paress" means, ranging from two minutes to as long as nine minutes.
In conclusion, then, one certainly is not required to begin eating his meal the split second after the recitation of Kiddush, and may take a few minutes as necessary to prepare himself. However, as the Aruch Ha’shulhan referenced the principle of "Lo Nitena Torah Le’mal’acheh Ha’sharet," that a delay is acceptable only because it would be impossible to begin immediately, it would seem that there is value in proceeding to the meal as quickly as possible, without any unnecessary delay.
Indeed, Rav Yosef Shalom Elyashiv (1910-2012) is cited as saying that it is acceptable to begin the meal several minutes after the recitation of Kiddush.
Summary: One should endeavor to begin his meal promptly after the recitation of Kiddush, without delaying more than several minutes.