Instead of creating complicated XP tables, leave it up to the DM. Depending on the circumstances, a table might not even have all the answers anyway.
To be vague about XP awards falls right into the d20 feel. I don't think I have yet seen a good run-down of example XP awards for non-combat in a d20 game. I always wing it.
I wouldn't make "Mother" a prestige class
. It's more of a Template if you ask me. This way it could easily be applied to any character as well. IIRC, there was something about Mothers in one of the pre-3e Dragon Mags. I'll have to see if I can find that issue and come up with a similar Mother Template for 3e.
@kolvar: re OGC... I know what we are making is going to be OGC and therefore officially part of the d20 system. I was referring to "official" as in "professionally" published. In any case, if we can use something from a accredited d20 source like Green Ronin for our little book, I think we should. This will keep things consistent. It also allows players who already have the green ronin book to keep their character the way it was and not be tempted by new material.
I started playing 3e shortly after it came out, so I created my character with just the PHB. As more material flooded the market, cooler stuff became available and I was stuck with some choices I wouldn't have made if I had had some of the newer stuff available.