Thank you for the tips and encouragement!
I feel a lot more confident about this project now, but if you could address one final question, I am still a little concerned about transfer of domain authority since one of the microsites gets top listings and nearly rivals the main site.
I realize domain authorities will by no means be combined, but I'm hoping the new inside pages don't lose so much page authority that they drop in the serps and, more importantly, that a significant impact can be made to the domain authority of the main site.
Basically, the main site is optimized and listing for our most valuable keywords and I'm hoping that the transfer of the microsite pages can provide a boost at the domain level.
Any insight would be much appreciated!