It's much to your advantage to check in when you get there (either online or in person) even if your room isn't ready yet. That way, Disney knows you are there and you can get all the paperwork completed. If you opt to not even go to the front desk via online check in, no big deal since you will be texted or phoned with your room number. But if you go to the resort to park, you cold just walk in, go to the front desk for check in (either stand by or online) and they will know you are actually physically there. Then, leave the car and your bags and take the Disney transportation to your park of choice and once you are done with your day, all you need to do is go back to the room as you don't have to go to the front desk for anything and it's something you don't have to think about all day.