You are also assuming that the planets you want to take over are habitable for life forms which is almost impossible right of the get-go...

First off, other stars are not as forgiving as the sun, they emit huge amounts of solar flares which are immensely radioactive and will kill any life form.

Second, does your hypothetical planet have breathable oxygen and an atmosphere that preserves it? Water?

Third, for humanity to thrive you need a whole ecosystem. Just sending frozen human embryos will not be enough, as we need food sources to sustain ourselves and those food sources need to be grown or also "cloned" i guess.