I really hate when the LFS pawns those danios off on people when they go in and get a set up. Its like red pill blue pill only with danios.
Sensibly, and morally (high death rates of fish in uncycled new-tanks) I'd have to say return them, cycle the tank, then go back to the lfs, if you still REALLY want them, get them, but i bet by the time the tank is done cycling you'll have a much firmer grasp on what fish you want to keep, and more importantly, what fish will enjoy your tank dimensions, and how much filtration you can provide as some of these fish can be messy, messy, MESSY.
Dont buy all your fish at once either, go in, choose your first fish, or maybe a pair, let them get established in the tank, see how the react to each other, their food, their environment. If it looks like these guys are going to rule the roost, perhaps not better to get anything more than a few filler fish.
Check out some of the links in old mans sigs, hes got good data for getting you on your way with a fishless cycle, making sure the actual physics of your tank and stand are in check (offset tanks can leak or even crack under uneven base pressure!). Help you with the water parameters such as PH, Hardness and even disease prevention.
Check out lots and lots and LOTS of data before bringing home a cichlid, not that any fish should be classified "better" over another, but you will see a HUGE difference between owning tetras, and owning cichlids or even one day if you get deep into it, marine/reef.
Good luck sir, post often, and in great detail (the more detail and pics we have, the more we can help) in the correct posting areas and youll get all the answeres you need!
Have a good one!
-TCG