Is the worship of God for Christians a family reunion?
It depends. There are some differences: not all of the family is here, at least not literally; worship here is weekly; and worship here is fraught with the challenges of sanctified people who are yet still sinners attempting to give proper praise to a holy God.
None of those things will be true in heaven, the eternal state: all of those resurrected in Christ will be present, it will be constant, and it will be perfect.
Even so, in many ways and in the truest sense Christian worship is a reunion, of sorts, though it is more appropriately characterized as "pre-union." With reunions, the family time together has passed, and its members reconvene to remember what once was. With "pre-unions," members of a body who never previously lived together convene in anticipation of a future time when all members will be permanently united.
Typically, earthly family reunions are scheduled together with the birthday celebration of the patriarch. Frequently that elderly relative is, well, elderly, and may be confined to the indoors or to a particular seat while the younger, more mobile and less arthritic members of the clan supervise the toddlers, tell spouses childhood war stories and secrets, and generally ignore the matriarch.
The patriarch, then, was a convenient excuse for all the others to socialize and enjoy the really interesting stuff.
If we are not very careful, our weekly episodes of Christian worship will resemble this family reunion, in which we gather ostensibly to celebrate the Patriarch, but find that our lateral, horizontal relationships and conversations are much more interesting than paying much attention to the old guy in the corner, who we think smells of moth balls, tells the same stories over and over, and is hard of hearing.