I would strongly urge you to consider not creating these as "sub sites" (aka Webs) and to consider creating them as Site Collections (aka Sites).
Reason being is that you won't be able to partition up your sub-webs into different Content DBs easily when they get big and unmanageable in one DB.
A whole Site Collection, including sub sites, can only live in one Content Database.
However, different Site Collections can live in different Content DBs ... which make them easier to manage long term as you can move them around more easily, have them on different SQL servers, backup/restore more flexibly etc...
- your sql admin will like you more when you dont end up with on large content DB :)