My DD (7) has been a character fanatic since she was 2, so we usually spend a ton of time with the characters. She doesn't care if she has just seen them at a meal, if she runs across them in the park she wants to get in line to see them again. In general, we have found that the in park meet and greets are a little less rushed and a little more playful than the meal meet and greets. We have the
Disneyland Kinect game, and I would say that your girls can expect some interactions like that. You can get hugs from pretty much all of them. Some are more playful than others. DD has danced and bounced with them, some have even played little games with her like taking her stuffed animal and playing with it or not giving it back or playing "hide and seek" with her, or "flying with her" or just numerous other little things. We have had some absolutely great character interactions, but it really just depends on the character themselves and the personality you get and probably the mood or way they feel that day. Some are absolutely incredible, some not so much.
As far as the meals, there just isn't much space around the tables. Sometimes it is just a quick autograph sign, photo snap and on to the next table. Sometimes you will get more interaction. Again, a lot of it is the mood and personality of the character. Akershus, there really isn't room between the tables for much dancing or spinning with the Princesses, but there are Princesses stationed around World Showcase if you want to meet and greet a few around the park that are often good for a twirl with a little girl. At Akershus, the Princesses do a little parade around the restaurant with the kids at set times, so hopefully that will happen during the time you are eating there. We've eaten there several times, and we have missed it a couple of times, but usually you are there long enough that it is done during your meal at some point. They will announce it to have the kids come join in. At Crystal Palace, Tigger usually can be enticed to bounce with the little ones. I think we got a a non-bouncy rush on by as fast as he could, Tigger once, but on the whole we have seen pretty good ones there. They also do a little parade with the kids here and there.
I just wouldn't make any promises as to what the interaction will be, and just let them experience it. Some of the characters will be absolutely fantastic, so much so that they can bring tears to your eyes watching the interactions. Some-not so much. We had a Cinderella at CRT when DD was 3 that was so bad that DD said that she was obviously a fake who had to stand in for the real Cinderella who was busy in Toon Town (before Toon Town was gone). This Cinderella clearly either did not feel well, or was extremely tired, or just didn't like her job. She basically wasn't interacting with the kids, to the point where she would ignore or be rude to them- very unCinderella like. She was the worst we have ever run across. It was kind of sad because Cinderella is DD's absolute favorite, but we saw the "real" Cinderella later and all was good.