Are Shiny Pokemon worth Evolving even if they have low IV?

If you don’t plan on catching more for the event, sure. If not, wait until the end. You might get something better.

It depends if you value a shiny over a pokemon that will perform slightly better. But you could evolve them just to get the shiny form in the dex. It's up to you really.

Depends on what you're out for really. I have a low-ish (40> ) iv shiny Charmander and mareep I got, but they are high level and I likely wont be powering them up after I evolve them to get their moves because I have very good iv versions im focusing on. In the case of my shiny larvitar, its got ~64% and 14 atk, so even though its over all iv's ant the greatest its level 35, its still going to be a raidwrecker like my 98% lucky nonshiny. If you're goal is to get a high CP shiny of the pokemon and the shiny you have is high level and If you know you wont be putting much candy into it, go for it. I'd say go for it if you want the shiny and its a pokemon you'd like to use/have, as I believe personal like of a pokemon >>> than any iv's.

But really IV's arent as big of a thing as people make them out to be, while higher iv's are better, in truth theres not some huge gap in preformance unless it misses some break or bulk points which even then, doesnt really have a huge gap as well.

If you have enough candy, you can evolve them just to show off in gyms.

Additionally, if you ever decide to trade them to someone, then the current IVs are irrelevant.

IV's are nowhere near the end all be all of this game. Given CP limits on the upcoming PvP, I wouldnt be surprised if sub obtimal IV's became "optimal" just to not break the 1500 and 2500 CP limits, respectively.
What's my point? Let's generously say that in 90% of battles, your IV deficit makes a difference (which is VERY generous; IV's are nearly irrelevant for most raids). That still doesn't compare to the 100% of matchups where other players are jealous of your Shiny CD mon, regardless of the IV's.
From a pure performance perspective... no the Shiny's aren't worth evolving. From a collector's perspective and from a social perspective, those shiny mon are more valuable than anything and everything short of a hundo non shiny.

IVs don't matter for the CP capped leagues, so sure, use them for those. Evolve starters and maybe Larvitar. The format, as of now, calls for teams of 3, so probably you might want two, and something to take care of whatever the mon you have two of is weak to. But if it isn't one of these, wait until we know more about PvP - we may find out that 0 stamina 0 attack 15 defense is best, or some other weird combination.

Only if you care about adding shinys to your pokedex, otherwise no.