Hello. There are no substitutions allowed with the dining plan, so no you will not be able to have an app as your entrée (I think this is silly of Disney, since the apps are cheaper than the entrees). Adults can order a kids meal, but it is a tremendous waste of an adult credit, though sometimes they will double the portion (the kids meal portions small, have gotten smaller every year we have been). What we did when my 10 year old wanted a kids meal, we just paid for that out of pocket and saved her credit. For every 2 meals we did that, we could add another TS and have 2 adult meals for DH and I, and just bought a kids meal for her. Worked great, and no one at the restaurants cared that we used a combo on credits and cash.