Last time we ate there, we cut through the esplanade to get to PPH for breakfast. We were questioned at security, since it was before the parks were open, but let us through. Is this the best path to get there?
Since there supposedly there aren't limitations on entering GCH from DTD, I would take the entrance into GCH (near Sephora) and exit the main entrance of GCH then head across the street to PPH.
Just know that when you go back, you'll have to head toward the Disneyland Hotel and enter DTD by Earl of Sandwich since you cannot enter the front door of the GCH now without a registration or ADR.
Only the ESPN Zone and GCH security checkpoints open at 5 AM to allow Hotel Guests to access Starbucks and similar breakfast options. The Mickey and Friends Structure opens at the same time the structure opens, and the East side check near Harbor opens around the same time as before the security changes late last year, so it depends if a Magic Morning is being offered. But they might get stuck there if they are there more than 90 minutes before the turnstiles are scheduled to open.