go with the tetras or cories, the goldfish get too big to live comfortably in a 29 if well taken care of. Goldfish also are pretty dirty fish(heavy bioload).
plastic
if all your worried about is making it easy then plastic plants and plastic fish
or a betta would be nice and happy with a 29 and a sponge filter
ok i want fish in there but what i have in there now is way too much work for my mom to take care of while im at college so im giving away/selling most of my fish like my 9.5 inch common pleco and getting fish that are cleaner than that monster and the other fish that are in there now. im just trying to decide what fish would keep my tank relatively clean yet still lively and cool.