If a person does not need to prepare any food on Yom Tob for Shabbat, must he prepare an Erub Tabshilin on Ereb Yom Tob? This can happen in a case where all the food for Shabbat was prepared ahead of time, before Yom Tob, or, perhaps more commonly, when a couple will be eating both Shabbat meals away, such as at parents or friends. As the purpose of the Erub Tabshilin is to allow preparing food on Yom Tob for Shabbat, would the couple in this case be exempt from the requirement of Erub Tabshilin?
The Ner Le’siyon (Rabbi Natan Ben Senior, contemporary) rules that in such a case one should prepare an Erub Tabshilin without reciting a Beracha. According to one view in the Shulhan Aruch, the Erub Tabshilin is needed to allow lighting the Shabbat candles, which is obviously done before the onset of Shabbat, on Yom Tob. Indeed, one version of the text of the Erub Tabshilin declaration includes the phrase "Le’adlukeh Sheraga," stating that the Erub allows lighting the Shabbat candles on Yom Tob. And thus, according to this opinion, even if one will not need to cook during Yom Tob, he must prepare an Erub Tabshilin to allow lighting the Shabbat candles. The Shulhan Aruch also cites a different view, that candle lighting is allowed even without an Erub Tabshilin, and this opinion is the position we follow, but nevertheless, one should satisfy all views and prepare an Erub Tabshilin even though he does not need to cook on Yom Tob for Shabbat. This is also the view of Hacham Bension Abba Shaul (Israel, 1923-1998), in his work Or Le’sion (22:6).
Summary: A family that will not be preparing food on Yom Tob for Shabbat should nevertheless make an Erub Tabshilin, but without reciting the Beracha.