I have a part of the yard that is incredibly rich top soil, can I plant them in the soil to give them the initial boost for a few years?
Sea buckthorn loves, loves, loves light and airy, nutrient-poor soil, the sandier the better. They handle dry spells, but not permanently "wet feet". Even the commercial breeds get little fertilizer, for home gardens it is recommended to fertilize for perhaps a year or two after planting, then let them mostly fend for themselves, except a light dose of compost evert other year or so.
But the really crucial bit about replanting them is - you probably won't be able to after a few years. They have a tendency to really anchor themselves and send roots (and offshoots) everywhere. And they grow fast! So better to think first where you want them, then plant. Amend the soil with lots of sand, if necessary.