Extending my stay in a motel

So im staying in a motel until i move in with my cousin. I booked it from last Thursday to this sat. I need to book it for another week, should i call front desk and say i need to extend my stay or should i book online. Also is there anyway i can check in early because i have work at 2 on sats and check in is at 3 and I'm going to have my cat with me and i can't just leave her in the car. Thanks