We bought at GF and have two kids a bit older than yours (4 and 6). Both kids love the splash pad area and there is a good variety of dining. I like the fact that it isn't difficult to get a reservation at the Grand Floridian Cafe so we don't ever have to worry about not getting a sit-down breakfast (unlike trying to get in at Topolino's- yikes!), and I also feel like there isn't as much competition for quick service meals since people aren't coming in as much from other resorts to eat. Riviera just felt really busy all the time to us.
And yes, as others mentioned, being able to walk to a park is SO NICE with kids this age.