In an article in the sefer Zeved Tov (a compilation of torah essays in honor of Rav Zevulun Charlop, former dean of RIETS, available here in .pdf format), Rav Hershel Shachter cites (p. 245) a number of insights from Rav Soloveitchik in connection with the Ramban’s comments to the pasuk “Zachor es yom hashabbos.” Ramban mentions that Shabbos must be distinct from other days in the week, similar to the Rambam’s psak (Shabbos 30:3) that one must have different, better food for Shabbos, nicer clothes for Shabbos, and even if one eats lavish meals all week one should change the time of the meal so as to mark Shabbos as special. Based on this idea Rav Soloveitchik frowned on the practice of making early Shabbos. The Rav felt that the motive behind early Shabbos is to have dinner at the same time as usual, to make Shabbos more like the rest of the week, contrary to the theme developed by the Ramban and Rambam. Making early Shabbos does not necessarily pose a problem in terms of hilchos tefilah, assuming one davens mincha before plag and ma’ariv only afterwards, but it does pose a problem in this are of hilchos shabbos.
As someone whose kids still grow cranky waiting too long for dinner, I sympathize with those who make early Shabbos. Looking at the Rambam, it is in the context of discussing what to do if you eat lavish meals during the week that the Rambam says to eat at a different time. If nothing else distinguishes the seudas Shabbos, than the time the meal is served will have to do. But for most of us the Shabbos meal is distinguished from regular weekday dinner in various ways, e.g. by what is served, how it is served, the fact that the family is eating together, etc. Where the meal is defined as special in other ways, I am not so sure eating earlier, even at the same time as usual, to avoid cranky kids is an issue, b'frat if it will be a more peaceful seudah in keeping with the Shabbos spirit. Hard to know what RYBS would hold without more information. (Haleva'i anyway that I should get home from work in time to make early Shabbos.)
(Update: By coincidence I saw in a local paper that RHS is a guest rabbi-in-residence somewhere and he is scheduled to speak between mincha and ma'ariv at their Friday night early kabbolas shabbos minyan. I think it's a fair guess that he is davening at the minyan he is speaking at, despite the sevara in the article. Make of it what you will.)