I'll add a few thoughts based on our experience with our three boys, but kids are all so different and I know it's so hard to predict their reactions.
Our two older boys have always enjoyed characters. But at age 2, our youngest son was absolutely terrified of any kind of local mascot or character - including Santa. He would burst into tears if he even saw one in the distance. We thought WDW was going to be the same, so we didn't initially plan to take him to character greetings, and we didn't schedule any character meals except for Garden Grill.
We chose Garden Grill for many reasons: this is our older boys' favorite restaurant and our arrival night tradition, so we didn't want for them to have to miss it. But it was also perfect for our then-2-year-old because of the way the restaurant is set up. The lower level has high booths, and it slowly rotates through scenes in the Land ride. So our youngest would have things in front of him to see, but could not see the characters until each arrived at our table. If he didn't react well, we could ask our server to have the characters pass us by and he would barely even see them past the high booth! This is different from other character meals, where he would have been able to see (and perhaps be upset by) the characters all around the restaurant, even when they are at other tables. Also, because the meal is served family style, he wouldn't have to get up from the table and walk past any characters on the way to a buffet. But if he liked the characters, they could stop by our table and we would all enjoy a character meal!
Anyway, when we arrived, we were amazed. While our youngest didn't like any other characters at home, he LOVED the Disney characters. We ended up spending lots of time at character greetings. I completely agree with the previous poster's suggestion of showing you tube videos, photos, etc. Our youngest saw lots of you tube videos and photos of his brothers with Disney characters before the trip. Anyway, Garden Grill was perfect for us in that situation, and might work well for OP.
P.S. I know some complain about the Garden Grill food, but we love it. We used to rate it just "good" as recently as March of this year. But during our most recent trip in July, we thought it was great - very fresh, all served family style (so no going up to the buffet and juggling plates with the kids) and quite yummy.