There's not a lot really close to the Marriott, but, if you drive to Crossroads, Jungle Jim's is a popular place, while at Downtown Disney you have the Rainforest Cafe. Head up to International Drive and there is plenty of choice at The Pointe (including X/S Orlando, which has a diner downstairs and a huge video arcade upstairs!), while Cafe Tu Tu Tango is another very good option. I would also recommend Wild Jack's (Western-style) Steakhouse, the B-Line Diner inside The Peabody Hotel (especially if you can time it to see the twice-daily Duck March!) and Don Pablo's Mexican Kitchen if your children are a bit older (say, over 10).