Ok, here are a few places:
1) Behind Ilikai hotel in Ala Wai harbor- lots of tilapia there, watch out kids get bored after having caught a few dozen or so (when they're hungry...) and get jaded the next time you go out. Use white bread and no sinker or float- its sight feeding hookups.

The curved side with the pipe railings just before the road to the ramp is where we go. Bathroom right there so it's convient. There's also lots of aholehole under/near the small bridge there and under the bigger rock near shore- good bait for the barracuda that hang out there. You'll also see some mamo, weke, balloon fish and the occasional kagami/white papio. Bring some pliers and a towel or you'll have tilapia crap (they pee/crap when you grab 'em) all over you.
I know, lovely, but, hey, its a fish....
2) Rocky area after Sandy beach- not as safe as a pier but lots of little pools close to shore that have hinalea, kupipi, mamo, humuhumu etc. My sons like to catch the small gobies in the tiny pools- he'll catch the same one over and over.... Use ika (last longer than shrimp) and a split shot. You can fish right near shore in the moving water and catch lots of stuff. Last time we were there I was pointing out a moray that came up to check out our bait and a turtle passed right over him- in 2 feet of water. Plus if they get bored you can look for shells/opihi, dig for crabs, catch sand turtles, go swimming, dig holes, make sand castles etc....More fun than a pier IMHO.
3) Might be too late now but if you get a chance on the next opening-sign up for cat fishing in Nuuanu. Good family fishing place. Just cast out (dunk) and polefish for the tilipia/cichlids there. Great fun- I invited 6 of my (2) son's friends and had a tililpia fishing derby complete with prizes (gift cards from McD's, Game Stop etc) and a fishing trophy(from Trophy House) for most fish followed by prizes for biggest, smallest, ugliest etc. Everyone won something and is sort of a regular thing with us-we just pass the trophy from family to family. Makes the kids real competitive but everyone has fun.
4) Ok, this is not fishing but reef walking. Find a minus tide(-.2 or more) on a dark moon night and go torching(reef walking) at night. You just need old shoes, a bright light(we use dive lights), a bucket and a couple of scoop nets. You just walk slowly along the shore in 1-2 feet of water and look for fish, crabs etc. We go near the old research station at Ala Moana starting from the sandy area going to the breakwall but there are lots of other places. You'll see all kinds of stuff- white eels, night tako, weke, hermit crabs, weird shells and nudibranchs. We just scoop 'em up and put 'em in a bucket, check 'em out and release 'em. Try it, it's fun and they get to see stuff that few people see.
Anyway PM me if you have questions.
Have fun, Randy