100% this. Could they have honored the 2004 team on some other random day of the season? Sure. Does it matter that they've chosen opening day? Not one bit.
And doing this gives most of his closest teammates a chance to honor Wakefield publicly too. I'm sure there will be speeches and stuff that they all want to be a part of. Combining them isn't inappropriate at all. It's a reminder of how fleeting our lives can be on this earth, and that for some lucky few like The 25 in 2004, the glory of their achievements can outlive them. A reminder to celebrate the wonderful things we've had in this life, baseball-wise at least, and to appreciate them all the more. It is a truly miserable, pitiable creature who can't view this event in that general vein, and has to come up with some reason to be upset about a memorial and a celebration of a triumph. Maybe the pakoras will be burnt, too!