I think what you're proposing is great, but I'm wondering if it's a bit early to think about donating your precious embryos? I say this from the perspective of someone dearly wanting a sibling for my child. It might be hard to understand this when you're so happy to be having one. A friend of mine also had a lot of trouble conceiving her second and we agree that it is harder this time around because we know how big the reward is. Why not give yourself a bit of time to get used to having one and see how you feel? If after that time you really truly don't want to go through another pregnancy, then how about a surrogate? There are lots of women that are keen to be surrogates but not only as a carrier (not using their own eggs).
I am just offering another perspective, no offence intended. FYI two websites you mind find helpful re donating your embryos are eggdonorangels.com.au and embryodonation.org.au
All the best.