We did the Ariel's Grotto character meal when our DDs were 4 and 6 (they're now 8 and 10). Compared to the regular princess meet & greets in DL at Princess Fantasy Faire, one downside to the Ariel's character meal is that you really only get enough time to take a quick picture, say hello, and then the princess moves onto the next table. At Princess Fantasy Faire, there was more time for our kids to have an actual conversation with each princess. There was a lot more interaction. We decided not to do Ariel's again after our 1 attempt at it. Our DDs have fond memories of it, but after spend ~$180 on the meal, we thought that our money next time would be better spent on other stuff at DL.
We also did the BBB thing. YDD (4 at the time) hated it because the glitter hair spray got in her mouth and she cried and begged me to take the bun out of her hair as soon as they were done putting it in. So that was $60 down the drain! LOL! ODD loved it, so at least for our family, it was definitely a very individual thing. We did the BBB appointment before Ariel's character meal. And I brought the princess dresses with us for them to change into. That part worked out really well.
If your DD wants to meet Mickey & Minnie with minimal waiting time, go to the Toon Town gate an hour after regular park opening (because that's when Toon Town opens). Then walk straight to Mickey's house and meet him without a wait. Then go meet Minnie - she'll either be at her house or on the "street" in Toon Town doing a meet & greet.