It's not walking distance, but it's really close. I love the Marriott Residence Inn SeaWorld. They include a nice buffet breakfast. You can buy dinner there too if you are back and don't want to go out (not that many selections, but my family always has found appealing offerings). We thought food was reasonable and tasted great. They have a nice pool and hot tub also (palm trees, so nice ambience). I love it that you have your own kitchenette. I have stayed in the double queen studios (nice layout) and in the two bedroom/two bath rooms (great if you want a little more privacy or have someone who snores) and liked both. They did a remodel just a few years ago and did a nice job with this. It's a big place and I like to request a place close to the breakfast area to avoid lots of walking as we'll be doing plenty of walking at the parks. This is my go to Orlando place if I am doing a hotel stay instead of renting a condo. This would be my recommendation if the rate seems reasonable.
The Renaissance is beautiful. I hate how expensive food is at those high end hotels, though. Breakfast is not included and we went offsite for dinner as prices were so high. Not sure if things have changed, but when we were there (sometime back) they charged for parking too. The lobby is really cool though. The pool areas are lovely (play area for kids) and adult pool has heated towels and cushy loungers (pretty sweet). It's walking distance to SeaWorld. Breakfast was not included either. I tend to these days avoid four star hotels just because I don't like the expensive food and add on charges even when I get a good base rate (my bean counter personality).
I have also stayed at the Hilton Garden Inn SeaWorld. It's just a little farther from SeaWorld than the Renaissance and is an easy walk to the park. This is your typical Hilton Garden Inn, so nice IMHO. Breakfast is not included, but a nice buffet is available (a little pricy). Dinner offerings are right at the hotel too that are reasonably priced and good. They have double beds not queens, so I would in your shoes pass on this one as there are plenty of double queen options.
If you want a condo and it's in your budget, the Hilton Grand Vacation Club SeaWorld is nice. If we are staying a whole week (Friday to Friday, Saturday to Saturday, or Sunday to Sunday, and want a condo we often for dollar savings will rent from a timeshare owner on TUG2.net or Redweek.com.