Apologies, US friends, this info is tailored to the UK! Please message if there's any info we can help with.
For both flights, accommodation and incidentals, we very much recommend using an Amex for the rewards. We have referral links for the Platinum card and BA Premium Plus card for you!
If you are looking to use AirMiles etc., we recommend using Reward Flight Finder (free trial available).
Regardless of whether you plan to stay onsite or offsite (more detail in Accommodation), we would recommend booking flights sooner rather than later. We have booked to fly out of Gatwick on Monday 15 February, returning Monday 8 March.
You can do multi-city flights with most carriers, but for some (eg, BA) you would need to call them directly to do this.
We have flown with both BA and Virgin to Orlando, and find them relatively comparable (with BA maybe slightly edging it on the flight experience).
Some flight-insights as follows:
Most Convenient
Direct with Virgin or TUI from Manchester or Heathrow to Orlando
or
Direct with BA from Gatwick to Orlando
~£600+
Most Economic
Direct with Norse Atlantic from Gatwick to Orlando
~£300–£450 (this is generally cheaper than connecting in the US or Europe, but you have to pay for baggage and meals etc...)
We will be kicking off celebrations on Thursday 18 February, so you might find more reasonably priced flights on Tuesday 16 or Wednesday 17. Monday is Presidents' Day in the US, which might inflate the price of flights, or (more likely) accommodation.
Typically I would recommend setting up Price Tracking with Kayak, Skyscanner and/or Google Flights, but trends at the moment indicate flight costs continuing to rise for the foreseeable.
Also, if you are waiting on Disney announcing their Dining Plan deals (typically mid-April), these are tied to onsite accommodation rather than flights (flights booked as part of a package either direct with Disney, or with BA or Virgin, aren't really cheaper than those booked separately in our experience).
Return Travel
Security queues at Orlando International can be long (in excess of 60 minutes). You can avoid this using MCO Reserve (free), which allows you to reserve a dedicated time slot for your party to go through TSA Security Screening up to 7 days in advance.
As with anything else, if we can help at all with this process for you, please don't hesitate to ask!
Walt Disney World
Around WDW (including from all Disney Reports), you can use Disney Transportation (buses, monorails, boats and the Skyliner) for free. We've always found this to be incredibly reliable (and good fun!)
Ride Apps
Uber/Lyft from Orlando International to WDW Resorts costs ~$50-80 each way, depending on time and size.
Uber/Lyft from WDW Resorts to the Universal Parks (including Epic) costs ~$25-35 each way. There are supermarkets and outlets along the route, for convenient trips!
Parking
All wedding guests have complimentary self-parking for the duration of the wedding events from 11am at the Grand Floridian. Security will be able to give you directions for where to park for the Whitehall Room and Patio. The period for free parking expires at 10pm on Saturday 20 February.
If you are staying onsite, you can get to the Wedding Pavilion on foot from The Grand Floridian lobby (approx. 5 min walk) by getting the Resort Monorail, or one of the boats, from Magic Kingdom (or walk along the walkway from MK- about 20mins!)
Parking for the WDW Parks and Resorts is complementary for WDW Resort guests.
Standard Theme Park parking for offsite guests costs $35 per day (you can move your car from one Park to another).
Parking at Universal Studios is similarly priced.
There are a number of vehicle rental options from Orlando International Airport.