We bought our tickets through Orlando Attraction Tickets for our upcoming holiday and have had no problem linking them to the My Disney Experience account. They did take a couple of weeks to arrive as they said they were waiting for stock to arrive from the USA. I normally check a few companies to see who has the best price when I want to buy. In the past I have used Attraction Tickets Direct and
Undercover Tourist.
As for Windsor Hills, we have stayed there 4 times now and are returning in July after staying at WDW for a few days first. I love the extra space, extra bathrooms and having a washer dryer! We find it close enough to the parks, animal Kingdom is the nearest, and there are plenty of restaurants and a Publix and Super Target nearby (for groceries). You will need a car though.
The properties are individually owned, so the standard of furnishing will differ. The last place we stayed offered daily cleaning (at a cost) but we opted for a few extra cleans so we didn't have to do much more than empty the trash and load the dishwasher after breakfast
Hope you manage to decide what will be best for your family, there are so many different options!