Is it permissible to forgo the second part of a vow – which is to invite friends for a lunch meal – due due to the difficulty of gathering them, after fulfilling the first part of it?

The Prophet, peace and blessings be upon him, forbade making vows because a vow does not avert anything and is a means by which something is extracted from a miser. However, whoever makes a vow must fulfill what he has committed himself to. A vow to offer a sacrifice (Udhiyah) is a vow of obedience that must be fulfilled, whereas a vow to invite friends to a feast is a permissible vow, in which the one who made the vow has the choice between fulfilling it or offering an expiation for an oath.