You can just as easily justify every federal welfare program arguing that you're taking care of the Founder's posterity.
I don't disagree with what you're trying to do, but I don't think you're considering the unintended consequences of the means you're wanting to employ.
As set forth in the preamble, the purpose and intent of the Constitution is to (among other things), "...provide for the common defence, promote the general welfare and secure the blessings of liberty to ourselves and our posterity." If they intended the document to be in effect for people born 200 years after its adoption, surely they meant for it to apply to those born within nine months of its adoption. Anything that would deprive persons (born or unborn) of the Constitution's applicability would be at best, inconsistent with, and at worst, in direct opposition to, the stated purposes of the Constitution, ergo, "unconstitutional".
IMHO, one must delve into the "penumbras and emanations," to argue otherwise.