Did everyone forget about Kappa Delta?
The sororities invited to my university would be :
KD, ADPi, Tri Delt, DG, XO, AOPi, SDT, AKA, SGR, DST (All of which are at my school now!), and ZTA, KAT, KKG, (I hear good things about these ladies)
The fraternities I would invite would be:
LXA, KS, SX, PhiDelt, SAE, SigEp,TKE, SN, Beta, DTD, APhiA, KAPsi, PhiBS
A nice even number of boys and girls...we have twice as many fraternities as sororities, but that's not a bad thing IMO!