No, my petsmart at least, doesn't carry floating plants...you can order them on aquabid...I get mine from p_voltain(?) ...name is something like that. Awesome seller! Has about 1000 plants for sale...a lot of floaters...red root is my favorite along with dwarf lettuce. Something really branching is good too...guppy grass or water sprite.
Your 5gallon should be fine for 6 fry...at least for awhile!)
You should get some live critters for your fry...a lot of time they don't know how to eat pellets (even crushed) and they can get some really good nutrition and exercise from live food...vinegar eels are easiest (you can get them on aquabid, too)...you just get a bottle(like a thoroughly cleaned spaghetti sauce jar); fill with 1:1 solution of Apple cider vinegar and water, add a piece of Apple and the culture of vinegar eels, cover with lid that has holes punched (or coffee filter and rubber band); put in a warm dark place like a cupboard or pantry...to use: pour some solution through coffee filter into cup, pour whats in cup back into jar, swish coffee filter containing strained vinegar eels in a bit of water, then pour water into tank with fry! As needed, replace fluid lost from jar due to evaporation...they don't smell, they are nematodes so wriggling, to naked eye they look like cloudy water.