I too hope you're feeling up for your project after your bout with the Stomach Flu.
Anyways, it is semantics but Lauan is not a subfloor; It's an underlayment. I only wanted to mention this so you're not misled. Lauan is essentially a 'cheap' material that gives a smooth, flat finished surface on which you can put things like vinyl. NOT ceramic tile. (That's cement backerboard.)
Anyways, if you're asking questions like that, how 'bout hiring a Home Inspector? Oh, and you can put hardwood flooring on top of lauan. Thing is, you'd want to be sure that there's a subfloor UNDER that. If there are more layers of other 'flooring' under the lauan, then the nails won't hold so well because the nails are meant to go DEEP into the subfloor; NOT the 'underlayers' of flooring and such. I hope I'm not confusing you.
I do wish you well. My best to ya and hope this helps.