Is there a time limit to how long we can be there? With Jake and Sophia by grandkids may not want to leave.
Like Love2Travel said, it's like other character meals. So Jake, Sophia, Manny, and Doc work their way around the room, one table at a time. They're staggered apart from each other, and keep moving at a pretty good rate, so while you likely won't wait too long between character visits, you won't get a huge amount of time with each one.
I'm not 100% certain they're still doing this, but in 2012, Hollywood and Vine did a little "dance party" with the characters every little while (maybe half an hour or so?), where kids who wanted to could come up and dance to a Disney Jr song or two alongside the characters. The characters then get back to business, starting where they left off and continuing to go from table to table.
I've never seen anyone thrown out for lingering too long... but they do need to keep the tables turning over, because the character meals are immensely popular, and even with ADRs, people often end up waiting for tables.
If your grandkids really love Jake and Sophia (so does my son!), they'll probably enjoy the Disney Junior Live on Stage show, which is pretty close to Hollywood & Vine, so it's easy to go from one to the other. The skits/puppets are cute.
