If it has a stove heating them up in 7 mins isn’t the issue….
 
Room for only 2 – 1/3 pans?  Wow….it doesn’t seem worth it to me.  Did you buy this yet?  How cheap is cheap?  I would probably just go with dogs and buns and skip the chili.  I just don’t see how you have room….or you could go with dogs and chili and just serve cold buns.  Not a great option.  OR….you could set up a secondary burner (camp stove using coleman type fuel bottles….or set up using a reg tank) for the chili or whatever. 
 
You also have to consider where are you going to be serving and how much volume can you get out in x amount of time.  Will the cart allow you to keep up?