Sounds good. Organic material will work wonders. You might add some bonemeal for future bulbs.

Sounds like you're on the right track. I think the biggest mistake one can make is not doing proper soil prep, regardless of what you're planting.
I would suggest going to the bulb forum, and doing some research on different tulips. Many of them are not reliably perennial. I can get Darwins to come back for about three years. I have large beds, so I usually plant tulips in groups of 100. Each year, there are less and less bulbs that come back. You may have better luck than I, because your soil is sandy, so they would be drier in the winter, but thought I would throw in that info for ya to chew on :) It's disgusting to spend a bunch of money on bulbs, then have them die off in a couple of years. I'm switching to more and more daffodils, for that very reason. I'm not getting any younger, lol and it's a lot of work to plant all those bulbs. Daffs are reliably perennial, and tend to make more bulbs over time, rather than petering out.
And, I love creeping phlox with iris'. Mine bloom with the early blooming bearded iris, and they love well drained soil.
Have fun planning your garden!
Brenda
PS..also, if you're planning on using landscaping fabric, do some searches on the perennials forum. There are many, many people who have put it down, or inherited in in a garden who really wish they didn't have it. I used it once, and I'd never do it again.