Is this Lapras worth powering up?

Of course it is, what is this question about even? I know many people at level 30 who still haven't found Lapras. It's probably the most sought after Pokémon in the game. You managed to hatch the best offensive moveset for it now being able to demolish any Dragonite you'll ever see. You should be beyond happy.

What Zureiyaa said. ^ I'm a level 34 and I still don't have a Lapras. Come on dude.

If it has the best moves, then it's definitely worth powering up, because who knows when (or if) you will ever get another one. I'm level 30.5 and I've only ever got one. I have it as my buddy because that's probably the only way I will ever get more candy.

I do not power up frost breath laprases for attacking
And I try to max ice shard ones for gym defense

But if your area does not give you a lot of lapras power up what you have

In my opinion, even if you power up, your CV value will not increase too much with these small amount of candies. And the IVs of this Larpras is a little low. Why not wait for the next one patiently. You have a long trip to achieve Level 40. I have a friend who got two Larpras by hatching and I got two Snorlax and one Larpras. So keep patience.
You can buddy up with it and accumulate enough candies. By that time, if you still don't find another one, you can power up this Larpras.

I'm level 29 and I have neither a Lapras nor a Snorlax. I haven't ever seen either in the wild. If I ever get one of these from an egg, you better believe I'm powering it up regardless of IV or moveset!