That's not much of a power draw. Your electrical needs will be minimal concerning putting together an electrical system for your bus.
I can understand you wanting to be able to plug in at campgrounds. Most of those have either 50 amp or 30 amp connections. The majority of people set up for a 50 amp connection, but they are probably running clothes dryers and other heavy draw appliances.
I'm not an electrician, but my electrical needs are about the same as yours. What I've done is to get a 50 amp to 30 amp dogbone adapter. The dogbone adapter plugs into this 30 amp by 50 foot electrical cable that goes to the bus. That will allow you to also connect to a generator, at a distance of up to 50'.
Most people don't buy a 50' 30 amp cable, but I don't stay in campgrounds much. I'll have a generator and can put it away from the bus if it's noisy. I can also run the 30 amp power cord from my house to the bus when I'm home.
As far as plugging the high amp extension cord into the bus, you'll find either RV or marine grade electrical plugs in your proper amperage that can be permanently mounted to the exterior of your bus in a discrete location on the left rear side of your bus. All these parts are readily available at RV stores or on Amazon and ebay. I found the best prices to be on Amazon. The marine grade plugs are noticeably better than RV plugs.
When it comes to the electrical boxes and things you'll need inside your bus, I am not the right guy to ask because I haven't made it that far with my bus yet.
You can get 32" TVs with blue-ray players that run off of 12 volt. It's not hard to charge phones from 12 volt systems either. I'm going with a 12 volt system as much as possible, which will require a couple house batteries to avoid using the bus battery. You can charge your house batteries off of your alternator, or you can charge from a charge controller when you're hooked up to the grid. There are so many options for power. It's good to be capable of being flexible for your power needs.
I like things kind of simple. I don't want to buy the charge controller or solar panels. A small set of (two) house batteries should be enough for your needs. There are so many varying ways to address your power needs in the builds on this site. You can get as complicated as you want, but it sounds like you guys have chosen to go the minimalist way like myself.
The less complicated the electrical system is, the better for me. I'm either plugged into the grid or I'm running on 12 volt. I do use 110 volt appliances like a toaster oven and double hotplate. I like a biscuit now and then. When I'm boondocking I use a butane gas burner that works from the cans of fuel. Each can lasts about 5 or 6 hours at about a dollar per can. No biscuits while I'm camping obviously, but I can fry the beegeebees out of some trout. I don't even carry a fridge anymore. Eggs last for a good number of days. Most everything else is fresh food. What needs cooling can go in a plastic cooler for a few days without needing more ice.
Subscribe to the KISS theory.