Well, you’ve given us the answer to the problem (assuming my great grandchildren — about 60,000,000 generations worth? — actually exist a billion or two years from now), and the answer is not the inconceivable job of trying to move the planet. Sure. Get me a big enough lever and I can move the earth. But it would be far, far cheaper and easier to block a percentage of incoming rays, not at the distant L1 Langrange location (where the diameters of the blocking bodies would themselves have to be truly humongous), but in simple earth orbit. Why make this fantasy scenario more complicated and difficult than it needs to be, except for the fun of it of course? For goodness sake, the technology for such a program is not so very far beyond our capabilities today.