Where is the Boardwalk? How do you get there (staying offsite)
The Boardwalk is one of the WDW hotels. If you are staying offsite you would drive there. Ideally use a GPS, but as you approach WDW, road signs direct you where to go.
The Boardwalk is located between Epcot and Hollywood studios. If you are going to that area for the evening, you can walk really the entire loop/area from Hollywood Studios to The Swan/Dolphin hotels to the Beach club/Yacht Club hotels to the back entrance of Epcot. There's a lake in the middle, and if you don't want to walk, there's a free shuttle boat that loops the entire area. If it is hot, you might want to take the boat.
Within WDW, you can generally get around for free via monorail, bus, and boats. Though getting around can be quite time consuming, and they don't offer direct transportation between most resorts.
If you choose to park at any theme park or the Swan/Dolphin, you will have to pay for parking. You might be allowed to park at the resorts, you might be given a time limit, you might be turned away.
I mentioned Universal earlier, and they also have many non-theme park areas to explore. Though you'd have to pay for parking. They also have free shuttle boats to all the hotels. Like the Disney hotels, each hotel has fun stuff to explore, including free afternoon activities at the resorts. Like Hard Rock has a giant video screen and they have afternoon activities for kids. I recall live music out by the pool. One afternoon at Portofino we found Scooby Doo.
I should also ad, while there is no admission fee to visit Citywalk or Disney Springs, it hard to escape either without buying anything. Disney and US are top notch at marketing to kids, and they also know their customers are looking for small items to bring home. The mark up on small items like pencils and candy can be crazy. I recall a $12 Minnie Mouse toothbrush! One potential way to resist is to visit a place like the dollar bin at Target before you travel. Another pre-travel item we've tried is pixie dust! Any kind of glitter hairspray of body spray- just don't spray it indoors! or it make s huge mess! but off WDW, it is only like $2 per can, which is nothing compared to BBB! At party stores, you can find all kinds of themed stuff, like stickers and temp tattoos. Within WDW, you might still find free stickers. (the DVC booths)
Even beyond the US and WDW hotels, there are a number of other very pretty (high end) hotels in the Orlando area. Some charge for parking. One the hotels near the convention center had real ducks parade through the lobby every day! Most of the higher-end resorts have really beautiful landscaping and fresh flowers. You might also find some relatively inexpensive fun snacks- especially if you share.
In Epcot, try visiting the free kidcot stations (in each country) and Innoventions sometimes has free stuff. (When last we visited, they were redoing much of it.)