Let me begin by saying that as I was trying to research the subject, I found few cited references as to why we should or should not celebrate Palm/Passion Sunday, from the argument that I lifted above to the argument that we are simply going back to following the Ancient Church's tradition of beginning the service with the reading of the passion, followed by the liturgy of the palms. If I can find better information with references as to where the information came from, then I will consider changing my thinking.
From a theological point of view, one of the greatest concerns I have with Palm/Passion Sunday is the concept that every Sunday is considered a mini Easter, a time for remembering the Resurrection. In fact, the 40 days of Lent does not count the Sundays of the season as part of the 40 days. While the 40 days of reflection is based, in part, on Jesus' temptations in the wilderness after having fasted for 40 days, we do not have the ability to go that long without being reminded of the Good News of the empty tomb.
Another concern I have is that by combining the two, we loose focus on one or the other. The church will either read the Passion narrative first, followed by ta focus on the Palms, or by reading the story of the triumphant entry, followed by the more overwhelming reading of the passion. Either way, it is hard to adequately address both in one worship service.
This Sunday, therefore, I am focusing on Palm Sunday. We will have the palms. We will sing "Hosanna, Loud Hosanna", and other songs of joy. However, I want to challenge people to come to our Maundy Thursday service the Thursday before Easter, so we can remember Jesus with the disciples the night he was betrayed. I want to encourage you to come Friday evening to remember the day of the resurrection, a service that will move many to tears, as we reflect on our own role in the crucifixion story. I want to invite you to come to worship Easter morning, as we move from death on a cross to an empty tomb and Jesus' revelation to Mary.
Let us make this week a week of true reflection, as we consider the gift of the Palms, the Passion, and the glorious Resurrection of Jesus Christ!