Take it from me - take the CFI-Glider first. You will need to take
your initial CFI with an FAA inspector or someone they designate (you
will not be able to just pick your favorite DE) and FAA inspectors who
are glider qualified are a way better class of people than the average
FAA inspector. There is no professional reason to fly gliders - those
of us who do, do so for the love of flying - and because of this very
few FAA inspectors are glider qualified. Those who are will not be out
to bust you for having a curled-up placard on the instrument panel.
Also, it's a lot harder to ground a glider than a power plane - lots
less stuff there.

It's how I did it, and I'm really glad I did.

Michael