irresponsible
untroubled
airy
blase
blithe
breezy
buoyant
careless
contented
corky
debonair
devil-may-care
easy
easygoing
feckless
free and easy
happy
happy-go-lucky
harum-scarum
incautious
indifferent
insouciant
jaunty
light
light-hearted
lighthearted
lightsome
nonchalant
perky
reckless
resilient
slaphappy
unconcerned
unworried
wild
boisterous
boyish
childlike
frank
good-humored
jovial
joyous
laid-back
playful
rollicking
sociable
sunny
thoughtless