You do not need to use grape juice. I know that honey has almost no nutrients and such for the yeast cells to eat. Most recipes I've seen have you throw in a teabag (for a few days), or grape juice, or whatnot to add nutrients to the must so the yeast can do it's work.
I personally go with Yeast Nutrient and Yeast Energizer. I'd suggest starting with a nice clean flavored honey (clover works great for this), and then adding mushed bananas to the secondary. FWIW, I'd also recommend you get Baby or Red bananas since (to my palate, at least) they taste more banana-like than the regular ones. Yes they are more expensive, but trust me on this. Also I'd suggest not getting them when they are green. In fact, I'd say buy them and then wait a good week before putting them into the mead. Let those skins get good and dark brown before using them (most recipes for banana bread suggest this, btw). Peel em up, toss into a zipper bag, mush and then put into the secondary.