Is dedicating Friday to performing certain social traditions related to a newborn, such as preparing their belongings, in optimistic pursuit of the blessings of this day, considered a forbidden innovation (bid‘ah)?

There is no evidence in the Sunnah for the desirability of singling out Friday with what was mentioned. This falls under the definition of innovation (bid'ah), which states: Every action that the Prophet (peace be upon him) did not do, despite the presence of its motive and the absence of any impediment to doing it, then doing it now is an innovation. Therefore, one should not seek to do that on Friday, or believe in its Sunnah status or its distinctiveness, for this is among the forbidden innovations, due to the Prophet's (peace be upon him) saying: "Whoever performs an action which is not in accordance with our matter, it will be rejected."