We want to drop off our luggage and use the parking lot and shuttle on Friday morning before allowed check in time, we will have a reservation for that Friday night, will this be allowed?
Yes you can.
Luggage drop off and using parking lot should be fine (it was for us, and reception is open 24hrs) but you will need to pre-book the shuttle; I assume this is the Disney parks shuttle. I suggest you email the hotel to pre-book and then you can confirm use of the parking lot etc. The KBF park is a 5min easy walk from the hotel / parking lot so no need for a shuttle to attend the park.
Get an answer from Knott's Berry Farm Hotel staff and past guests.