Flight lands 3:45, off plane at 4:00. Baggage pickup, 4:15. Which means you'll be hopping on your shuttle around 4:15-4:30, right in the heat of rush hour. I'd plan 90 minutes from LAX for rush hour, making it 6:00ish when you check into the hotel.
Assuming your flight isn't delayed, and there's not a bad wreck during rush hour, and you don't take the DL Resort Express (I've waited as much as 2 hours for them before, and then been stuck on their bus for another 2 hours!), the ADR should be fine.