OK, what time is your PCH Grill reservation, and what day (date) are you visiting? That would really help. Also the ticket you will have, a Military Salute, a 3 day SoCal ticket, or something else?
As for driving, I would take the Carpool lane from when it starts in Dana Point/San Clemente all the way to the Gene Autry Way carpool exit, turn right on Gene Autry, then a left onto State College Blvd (not going straight into Angel Stadium). Then go straight up State College over Katella Avenue to Ball Road. Make a left on Ball Road, and then a left on
Disneyland Drive (Past Harbor). This will give you easy access to both the Mickey & Friends Structure and the Paradise Pier Hotel parking lot. This will have some traffic in the AM, but better than other possible routes, and maximizes the use of the Carpool lane.
As for security, currently the secure zone is both parks, the Main Entrance Plaza and ticket booths and Downtown Disney. To enter that area, you will have to go through a bag check and a metal Detector, basically nothing that can be used as a weapon, including glass bottles. You can go to the Disneyland website for the full list of banned items.
https://disneyland.disney.go.com/park-rules/
On the east side (Harbor Blvd), there is just one set of security check stations. But on the West Side (the one you will be using, unless forced to park at the Toy Story Lot), there are now a set of them (5 different locations). The two that apply to you are the ESPN Zone checkpoint on the West Side of Downtown Disney, and the one next to the Mickey & Friends Structure. (the Security check is part of the tram loading process).
Now, if you can park directly into Mickey & Friends and want to walk to PPH (once again, depends on the time of the PCH Grill reservation and when the park opens (which is how we know when the Theme Park parking lots open), and IF they are parking Mickey & Friends first thing (no way to know until that morning), you do not go through security at the structure, instead follow the signs to Downtown Disney and the walkway provided. You walk past DtD to the Paradise Pier Hotel (once again follow the signs), and you will feel like you are swimming upstream as the Hotel Guests head to the park. Find the restaurant and check in for your meal. After the meal, those who plan to walk to the parks head back up the path to the west side of the ESPN Zone and go through security there and head east to the Park Entrances.
If you need or decide to park at the PPH first, just follow the signs on Disneyland Drive heading south from Ball, and pull into the entrance, and follow the self park signs to the west side of the hotel and its small parking structure. Go to your meal, get the parking ticket you got when you entered validated, and then decide if you want to pay the higher price to park ($58) or move the car. Then it is the decision of the whole group getting back in the car,or spliting up. If you split up, the walkers head to the ESPN Zone (follow the signs pointing northward) and do security and walk to the parks.
For at least the driver, get back in the car, and exit the lot. you are forced right (south) on Disneyland Drive, make a right onto Katella, and then another right onto Walnut, and take it all the way to Ball Road, and make a right onto Ball, then back onto Disneyland Drive, park at the M&F lot is open, if not follow the signs and police officers direction to the other lot, more than likely the Toy Story Lot. After you park, you board the buses to the east side entrance, and after you de-board, you then go through Security to enter the parks.
To go home, board the bus/tram that will take you to where the car is parked and head home. (follow the signs to the I-5 south, and get back into the Carpool Lane.)
So if we can get the actual date of your visit and the PCH Grill reservation time, we can help you figure out of parking directly into the M&F structure is an option.