porn blocker question

so, i'm not a total newbie, but have a newbie question

i'd like to install a porn blocker, to keep me straight and protect kids,
but would prefer something running totally in the background,
not yet ready to confess anything to wife, though someday, with a good bit of clean sailing i hope to.

anyways,
does k9 or covenant run in the background where no one would no it is there, till it blocks a page?
or is there some kind of icon on the toolbar, that may induce the wife or kids to ask, hey, . . .whats that?

thx
vizsla

 

ok,
so i just looked at both website, for k9 and covenant eyes,
one's free, i don't mind paying to covenant eyes,

looks like neither are totally ilent where wife won't know its there,

so
perfect cover story and timing is:
on a friend's recommendation, i DID let kids watch guardians of the galaxy, movie, last night, which had a bit more foul language than whet we allow them to see/hear.

so i tell wife i feel bad about that, and we need to install some safety measures on internet, (which we have discussed several times.

can you use both at the same time? is there a need?

i like the tracking idea, of time spent, as i think my kids get way too much tv, and way too much time on the computer,
i am hoping covenant eyes will track how much time a day my son is on mine craft.

your experience/comments welcome, please

 

MAIN QUESTION:
how do they work with private browser functions, which do not keep a cookie or history of websites visited?