You are given 90 minutes to complete your meal - that should give you sufficient time to meet all the characters as for that breakfast you will likely only see about 5: Mickey who you meet upon arrival, Daisy, Minnie, Pluto, Stitch and maybe another, we saw Max there both time we visited.
We found we were pretty much done in about an hour - the kids can get up and dance too - so it's as much as you want to make of it.
The other issue is if your reservation is for say 8AM - you might not get in right at 8 - we have had to wait at least 15 minutes for both our reservations at Surf's Up. So keep that in mind if you need to be somewhere after the breakfast.