Goldfish will not inherently destroy plants. They have a tendency to, but it is not a definite. The biggest issue is keeping the goldfish full on a high quality diet that provides everything they need so they don't have a craving for the plants. I use NLS and it does that for mine. The only other diet I have heard of that also does this was used by someone on a goldfish forum who makes her own gel food, so she could put everything needed in it. I have not heard of any other diets doing this.
Many plants are great possibilities. All of my tanks have relatively low lighting. My 75 has just under 1wpg and the plants do very well in there, especially when I had all my fancy goldfish in there. The plants love the waste from the goldfish and help keep the tank cleaner between water changes. Plants that have worked for me include: anacharis, moneywort, water wisteria, vals, moss balls, cabomba, and many others. I suggest just trying out whatever your LFS has, see what works.
Yes, that tank size is an issue. Please check out the articles in my blog on goldfish (seems you already have), and a newer one on stocking an aquarium.
All my tanks are planted and all have Estes' Marine Sand as a substrate. I use the following Flourish products as the only fertilizers (nice and simple): Tabs, general liquid supplement, and Iron (a few plants showed signs of iron deficiency).