I absolutely adore Goofy's Kitchen (breakfast, not dinner). The buffet is huge. There have been so few times over the years that I, personally, have had less than great service or food that was sub-par that I really can't even remember when they were, at least not the individual incidents. I think there are 'off days' like at any dining establishment. My overall experience with the GK character meal has been great.
Lately, there have been some not-so-great reviews of Goofy's on the DIS, but that happens for every DLR restaurant at times. Still, it's a lot of money to spend so you might not want to risk it.
If you really want to see Mickey at a character meal, the only place to find him will be at Surf's Up. I don't think Surf's Up is too much cheaper than Goofy's, so if having a variety of food is important I would go to Goofy's. I have read both good and bad reviews of Surf's Up, just as I have for all of the other character meals too.
Goofy's may have anywhere from 5 - 8 characters onsite (including one at the entrance), while Surf's Up generally has no more than 5, from the photos I have seen, and sometimes only 4.
Minnie & Friends in
Disneyland has the most characters out of all the character meals at DLR - and it's cheaper (slightly) than Goofy's and Surf's Up, if I am not mistaken.