We use history as our core and work out from there. It is where DS's passion is at the moment.
I have SOTW and History Odyssey Ancients. I use them really loosely though and more for inspiration and maps. I pull lots of science into it - learning about period science, doing variou science experiments, etc. I also take it on from a literature based standpoint, so we do lots and lots of reading/language arts. Math is really the only "seperate" study. But depending on their ages, you can pull in cool egyptian math games or something similiar.
We use the Usborne World History ILE and the Usborne Ancient History ILE as our "spines" - we sit and pour over those for hours, he reads them on his own and drags them around with him cuz he loves it so much. SOTW - honestly the most we use is the Activity Guide and the audio CD. He does have the book, which he reads to himself but we rarely read it aloud together. It is nice little stories - but the meat of it is the Usborne books for us. LOTS of documentaries and videos too - Walking with Dinosaurs/Prehistoric Beasts/Cavemen were HUGE hits here. So have been the various Egypt vids we have watched (thank you Netflix!)
So far, we have done
early prehistory - learning about dinosaurs, ecology, evolution, carnivore vs herbivore, predator vs prey, extinction, natural events such as earthquakes and metorites, climate changes
We did lots of dino projects including a dino dig project he loved, evolution stuff, watched lots of vids, and read lots of extra dino books (including stuff like Magic Tree house and Magic School Bus)
prehistory - dawn of civilization - learning about the evolution of man (LOVE walking with cavemen!). We also made paper "spears" and hunted mammoths (stuffed animals or occasionally the cat LOL). Got leather from the craft store and banged holes into it, threaded leather cord thru to make a "game pouch". Got some plastic stretchy lizards at target and used out play kitchen food too - hidden all over the house so that we could forage and hunt (all going into the game pouch of coarse). built tents/huts out of chairs and blankets. Talked about the benefits of settling down and farming...learned about growing cycles, seasons, plants vs animals. We did plant experiments such as dying carnations (water absorption), planting seeds and watching them grow, collecting and recording rainfall....Also studied the differences between plant and animal cells and made each using jello and fruit for organelles - what a yummy science project that was!
Mesopotamia - lots of reading, building cities and zuggarts out of blocks, art projects - especially clay since they invented the first potters wheel (and then the wheel for carts), making lego cars (first invention of the wheel), seasons and months (first calendar), mythology studies, lit studies (like reading abot Gilgamesh) music (hysterical They Might Be Giants song We're the Mesopotamians - never heard of Arshinbanipal so we had to find out who he was)
I also include language arts as we go - reading lots of supplemental books strengthens language and vocab skills. You could easily do vocab and spelling lists from the various units - especially using something fun like Spelling City online. DS expressed interest in learning about nouns, verbs, etc - So I'd copy key idea pages from SOTW or the Usborne book and we'd diagram sentences for the fun of it. Lots of his creative play and art projects naturally have been related to his learning topics (not due to prompting either!!). SOTW and HO both include coloring pages which we don't use and maps, which we do use. So he is learning ancient geography, the evolution of geography over time due to social changes, and how to read maps.
Personally, it works really really well for us - and it is easier than trying to follow other curriculums or mesh things together. It all relates, and therefore it interests him. I like that he is learning a more holistic approach too. Not many 5yo read about the adventures of Gilgamesh or play act them LOL