Rental car is the most flexible way, and it's my preferred way. Of course, I always rent a car for my entire stay, but that's another argument...

This is a common situation, and the most common solution is a one-way rental.

Rent from Alamo or National at MCO for two days. Use the car to get from MCO to the Wyndham on Friday, then use it on Saturday morning to get to WL in the morning to check in and pick up passes, then drive to Epcot for the day (you will have to decide whether you want to leave your luggage at WL all day, or leave it in the trunk of the car). At the end of the day, drop off the family (and luggage) at WL, then return the car to the Car Care Center, which is just on the other side of the MK parking lot from WL. Alamo/National will shuttle you back to WL after you drop off the car. Cost of the rental should be somewhere in the $100 range.

While you have the car, you also have the ability to go off-site for shopping. Snacks, bottled water, any forgotten items like sunscreen - all of these items can be found at local Walgreens stores at far more reasonable prices than those of the various on-site options.

Then there's the possibility of going to one of the Disney outlet stores in the WDW area, such as the Orlando Premium Outlets location about 1/2 mile from Downtown Disney. It's a 10-minute drive from the Wyndham; you could stop on the way from MCO and do a little browsing, if your plane lands early enough on Friday night. Or you could take a mid-day break from Epcot on Saturday. Or, you could keep the car an extra few days, if it's in the budget.

Just keep that scene from Die Hard in mind: "The Car. Send in the Car!"