My daughter and I recently ate at Garden Grill and it was just lovely, one of our better character dining experiences. They will indeed bring a second portion of any food you've been served on its own, as we did this with several items and our server's reaction when I asked her didn't seem to indicate this is an infrequent request or anything difficult for her to accommodate.
As for asking for an item to be left off your initial plate, I would say that might be a little more hit and miss. If you would like to avoid wasting food and ask for an item you know you won't be eating to be left off the plate, I would ask right away to give your server and the kitchen plenty of lead time on the request. I imagine that the plates are being prepared automatically as seatings in the restaurant are occurring, so you would need to head that off with an early request.
We sat on the upper level, which was very good for us. My daughter loves to watch the characters even when they are interacting with other people, and you have a pretty good vantage point from the top level to watch them greeting everyone around you. On the other hand, if you have one or more kiddos who are likely to be antsy if they see characters around and that might be distracting for them (or if it might make them too sad or impatient) you may want to hope for/request the lower level. I think it's probably a little harder to see the characters walking around at the tables on the upper level from down there, so they wouldn't be distracted by seeing them out and about when they are not soon to reach your table. I think the view of the backdrops on Living With the Land is roughly the same on the upper or lower level, with the lower level able to see just a tad bit more of that.
We really loved our dinner experience there. I hope you have a good time there too!
