I've been a receptionist, and I've been an office manager - if you have the choice, go for office manager! Depending on the size of the office you basically still are the receptionist you just have a lot more responsibility. For me, the hardest part of being a receptionist were the days where I had basically nothing to do but still had to sit there and look pleasant. If you work in an office where you can wear a Bluetooth piece in your ear, you can listen to podcasts which takes care of the monotony aspect.
The other hardest hurdle for me is not letting details fall through the cracks. I have come up with some checks and balances systems to make sure nothing gets forgotten, and obviously I write every single thing down as it's asked of me. I cannot rely on my brain to just remember a task someone asked me to do. I make a lot of lists.
You can also fill downtime with stuff like an online typing class which just looks like you're sending emails or whatever from the outside. Sitting and doing nothing is just too hard.
For what it's worth, I know they're the same in the DSM now, but I'm not hyperactive. If you are, being a receptionist might not be for you.