This may be an unpopular opinion, but I just did the Bon Voyage breakfast at Trattoria al Forno last week and it was the most underwhelming character breakfast. The only character meal I have done that is worse is Hollywood and Vine for dinner. The pastries were stale, the food was not good (pancakes were like lead), coffee was weak, and the characters besides Ariel sadly fell flat. Flynn basically said "hi" and walked away. Everything I had read from multiple sources (even including this thread) said this breakfast should be great so I am hoping I had an off day, but I just felt I should share my experience.
I watched the DIS review of Topolino's because I had it booked for the spring, but was reconsidering it after my less than stellar December character breakfast. I am still on the fence, but the characters really looked cute and unique. If your granddaughters have a favorite, Riviera even sells plush versions of each character in the special costume.
The Riviera is the first stop on the IG line before it goes to CBR. It could be nice, but depending on the time of your breakfast, IDK how crowded it would be with people heading to parks. If you're hesitant to try it, the drive wouldn't be far at all.