Future generations should adapt just fine. You're not going to have a distinct 'race' of Martians for tens of thousands of years; it took 60,000 years just to make the different races on Earth, after all.
As for Venus, terraforming would be a LOT more involved than any other potentially habitable planet in the solar system. On Mars, you just have to add an atmosphere; on Venus, you'd have to take away an atmosphere, and currently the only way we know how to do that would devastate the entire planet.
Unless you can make something that can withstand atmospheric pressures equivalent to the bottom of the ocean, is hot enough to melt lead, clouds of sulfuric acid so dense we can't see the planet itself, and molten glass raining from the sky in hurricane force winds, Venus isn't worth the effort. We can get the same resources on Mars, the asteroid belt, and the Jovian moons with less trouble.
We'll be able to do it, it just won't be practical for a VERY long time.
Valid points. Radiation on Mars really isn't an issue, particularly in the long-term.
Comets are mostly ice; you've got oxygen, hydrogen, and water vapor. Good start for an atmosphere. Huge mirrors in orbit could be baking the water and CO2 out of mars' crust and heating the surface in the process, which would add to the atmosphere and make it more habitable.
Really, the biggest hindrance to inhabiting Mars is the dust. Read up on the issues lunar dust presented, and now figure out how all the dust and wind on Mars is going to create problems. Even with radiation, heat, and atmospheric pressure solved, a Mars colony is going to need airlocks every time they go outside, at least until they have enough plant life on the surface to anchor the soil down.
We're gonna need a hell of a lot of grass on Mars, and wind breaks too; even then, it's gonna be a global dust bowl.
There's literally millions of 'em in the outer solar system, some of which pass through the inner system every so often. Send some drones out to snag a few and aim 'em at Mars.
I don't think you understand what would be involved in terraforming Venus. You have to thin the atmosphere; it's so thick that you could literally fly by flapping your arms. You'd have the same pressure on Venus that you do at the bottom of the deepest part of the ocean, which is more than enough to crush you like a tin can. The atmosphere is poisonous and full of acid. Any machine on the surface couldn't be solar powered, because the clouds of acid are so thick that no light reaches the surface and we can't even see what the surface looks like. And solar is a major part of why Venus is so hot, because it's closer to the sun than Earth is.
Venus is probably the most challenging thing to colonize in the solar system, and it just isn't worth the effort. Worst case scenario, we can drop robots to the surface and have them mine for resources and launch it in rockets so we can retrieve them, but that's still more effort than it's worth until and unless our technology advances significantly, even beyond that necessary to colonize Mars and mine the asteroid belt.
You're not taking a breath on Venus unless you want to die. Its atmosphere is carbon dioxide and nitrogen; everything else is present only in trace quantities, not enough to breathe. And it's still full of sulfuric acid.
If you floated in the atmosphere at the point where the temperature and pressure were both survivable, removed your helmet, and took a deep breath, you'd immediately start choking, go blind, and pass out from oxygen deprivation/poisoning. At the very least, you'd need to be wearing an oxygen mask.
And radiation shielding, because you're at the top of Venus' atmosphere and there's no magnetosphere protecting you.
You're not even comparing apples and oranges, you're comparing apples and clowns.