I've read that the biggest problem with sandy soils is leeching of nutrients. So how should you approach sandy soil when you establish your garden? First take your time and do the double digging.

I'd broadfork or pitchfork the soil to break up compaction then do the standard sheet mulching. More often than not there's some compaction that you want to break up and aerate before you establish perennials.

It's also not the worst thing to till marginal and/or disturbed sites if you are establishing a long term garden.

Often you are working with pretty degraded and compacted land and tilling can restore some better conditions.

Just remember that tilling is a major disturbance and you'll need to restore the biology afterwards so doing a good top dress of biologically active compost before sheet mulching is a pretty good idea.

Organic matter is going to help with the biology and biology is going to help with the beach. I don't have tons of experience with sandy soils but my understanding is you can turn them fairly easily with soil ecology. The main thing is getting good compost out.

Most soil organisms aren't going to move much more than the top two inches except for fungi which will colonize anything wet and aerobic enough to support them. So build a lot of fungal foods into your mulch layers.

I think I read you already had a lot of wood chips and sawdust out so that's a good start.

The solution is to start with biochar before layering/mulching. This reduces the need for additional nutrients over time because the biochar retains the nutrients that would otherwise be washed away. I've not tested this theory but it would be worth reading up on as it could save you a lot if work. Here is a great video I found showing how to make your own biochar.

Still the science isn't totally in yet. Here's a study to watch: