Are they worth to power up?

Well, that depends of a lot of things.
Do you need those mons?
Why not evolve?
Move set is good but CP will be higher.
If you find yourself using them... then I think you should not evolve them.
But if you find your self not using them and don't need the candy for anything else... go ahead and evolve all of them!

Venusaur is one of the coolest mons in the game and you have one with good IVs and B rated moveset both in attack and defence. Only if you think you can find a better one soon (I dont think so even if you live near a bulba spawn) you can consider not to power it up. If not, it is worth the stardust and still can crush all the water types.
Actually we shouldn't be that much competitive. That kills all the fun. Try it in gym and if you like using it then why you shouldn't power him up?
And it would be better if Golem has rock moves instead of ground. If you dont need an attacker with ground moves you can just keep it for another time.

A Venusaur with those IV's and that moveset is in my opinion a prime candidate for powering up. The only reason I wouldn't is if you already have 2-3 really strong grass pokemon (and I wouldn't count Exeggutor in that).

The Golem on the other hand... You've got yourself the pokemon & moveset combo that is the best Ground type attacker in the game with good IVs. The problem is that Ground Type attackers aren't particularly needed. I would keep it but not power it up on the off chance that something happens to the gym meta and a Ground attacker is a good thing to have.

I'd power up the Venusaur

I'd keep the Golem and maybe Power it up Later when Generation 2 comes out and the Electric Pokémon Ampharos 2618 is available in Gyms.

In fact, Generation 2 will be game changing mostly in the Sense that there will be Powerful Electrics in the game. Lanturn with Water/Elec is also going to be the great Vaperon/Lapras Bane.

I'd happily take the Venasaur off your hands :)
Power it up!

Golem is just too niche at the moment.