Ah congrats Megan, I wish you all the luck in the world.
I have been to Salou several times and have on a couple of occasions booked a last minute deal.  I have had no problems finding something suitable.  My last booking was for last September, 11 people ranging from 1 - 47 and we had a great time.  We stopped in the Best Oasis if that helps.
Let me know if you want any information.
Sue x