I gave my seven year old daughter a 10g. She has a male betta, female betta, 4 zebra danios, 2 plattis , 4 guppies, and 2 or 3 I don't remeber. They all get along well. Maybe you can get some ideas from that.
I did see some dwarf gourami today and they were all cute and sparkly. I guess it depends on the age and emotional maturity of the child. I wouldn't want a kid to be totally indifferent to the fish, either. They would be awfully pretty with a few little cories in there.