Have to agree, definitely don't go down the "used" tickets route. Buy them from one of the major attraction ticket sellers online like Keith Prowse. Definitely shop around though. I agree, no real need for any other tickets apart from the Disney and Flex. You are well covered with those.
I can't comment on transportation from Sanford as we always fly into MCO. Have you thought about hiring a car for your stay? There are lots of fors and againsts driving in Orlando but I am definitely in the former. It's a breeze and opens up so many more options for you, especially in the evenings. Maybe worth a thought?
Also can't comment on Amtrak down to Tampa although we have used them extensively on other routes. Journey time seems long though, certainly compared to driving but I would add that despite the often harsh criticism afforded them by the US public, they are far superior to any train provider we have in the UK. The trains are well maintained and very comfortable, and the staff actually care about you. I think it's a nice way of travelling down, but of course if you had that car.......
My one word of advice is don't burn yourselves out. Easily done in Orlando. There are often a lot of laughs about how much of a military operation planning your 2 weeks in Orlando can become, but it is true and spending some time before the trip drafting up a plan of action can save you time and hassle in a lot of cases. Definitely plan for rest days after the big parks, and make sure you get there at opening for all parks...it's amazing how much you can fit in during the first hour if you are on the ball. Although a lot of people favour the early start and head back to the hotel/villa for a rest/swim before going back to the park, I don't necessarily think that is the right thing to do, and without a car it is virtually impossible. Of course if there is a fireworks show, or something you want to see later in the day then it might be worthwhile arriving later, dealing with the crowds initially and taking advantage of fewer people the long the day goes on.
Costs? Difficult to judge but Orlando is still cheap compared to a lot of the USA. At any chain restaurant you can get by on $10 for an entree, which is often big enough to keep you happy. Add in a dessert of $4+, drink and tax, and I would budget $20 evening meal budget per person (we always budget $50, whereever we are in the USA). Breakfast can be as cheap as you want it. Even a buffet is only going to be around $6 per person, try and grab vouchers out the booklets if you can. Lunch in parks? Pick a figure out of thin air. I find most entrees in parks are the same price as an evening meal, so tend to avoid eating too much in the parks because the value is just not that great.
Not sure on travel costs as we always have a car. It's going to mount up though. Are you staying in a hotel which provides park transportation? That will obviously help.
I hope this has helped a bit. If you need any further help, I'm sure we can help.
