Hey Scritchell, make sure you check out the Disney Dining Plan (depending on which hotel you're planning for). It's one of the best reasons to stay on property as a UK guest, especially when it's free! We've never done without it and it was saving us $200 a meal (5 people). Disney Travel company (the WDW website) is the best way we've visited (the first time we used it, they gave me a free plastic rucksack with colouring etc to keep me entertained on the flight, 10 year old me was set!)
If your son is more into thrill rides then UpAllNight may have a point about staying at Universal, however we're not, so staying at Disney works out the best. Being able to just take a bus back to the resort for a power nap (especially on a three week trip) rather than schlepping back to an off property hotel (there are some Uber drivers who will take advantage of you not knowing the roads/area and therefore take a longer trip to charge you more money/get stuck in traffic on purpose for the same reason. Your accent will standout). All of the resorts also offer Disney activities so you're never out of the magic (movie nights by the pool, some hotels have characters at breakfast)
On our last trip last May, they were doing a lot of construction to we believe install disney specific bus lanes on all the major routes in and out of the parks to improve those wait times (they can be a pain if you've got a reservation, hence the introduction of the Minnie vans)
For maps, check eBay. I was on there two days ago and people were selling full sets of park maps. To get an idea of Florida in general, there are SO MANY Orlando YouTubers. TimTracker is a great one; they did a video last week of visiting all the major theme parks in one day so that would give you an idea of how far away from each other they all are (9 theme parks took all day, only doing 1 ride per park) and nearly every current video is from a Theme Park of some sort. But a lot of the Orlando Youtubers know exactly why people are watching them so they're a great way to learn tips and tricks and secret nuggets of information. They will also do resort tours and some are able to do room tours as well, so it's a great way to visualise how things will look/work.
Recommendation: get yourself signed up to the Virgin Flying Club. They have a feature called Shops Away which allows you to earn flying miles when you online shop, which can seriously bring the cost of flights down. Even something as simple as ordering a pizza (both Dominoes and Pizza Hut, and maybe Papa Johns also) can earn you up to 2 miles per £1 spent, and some retailers (there's a lot!) will offer sometimes up to 10 miles depending on what they're selling. So long as you go to the retailers website via the Shops Away site first, you'll earn, and some retailers are now working with Virgin and major payment cards like Visa and MasterCard where they'll register purchases made in store too. Tesco Clubcard points can also be converted into Flying Miles as well.
And that's the end of the information dump! We do a ton of research, and yeah the BritGuide is the best for UK visitors (I believe they update it every year, lucky so and sos getting to go so often), but if you want to chat some more let me know. We're already planning bits and pieces for 2021!
Be prepared to change things on the fly. Rides go down, kids get tired/hot/cranky etc etc etc regardless of how old they are, people are rude (they just are, you can put the people in the magic, but you can't put the magic in the people). Also, enjoy the planning! When you've made the announcement, get your son involved! It's a great way to spend a Sunday morning/whole day watching videos and making plans, it builds the excitement, and maybe plan some surprises too.... Disney can make a lot of things happen if you know who to talk to (2 surprise cakes under my own belt)
how long are you visiting for?
