Is there a way to change the family funds without loading that family?

Oh how did I miss that. One way I can think of would be moving them out (selling the furniture = leaving it in the house), adding one sim to the household via manage households, making a new household for the original sims and finally moving them back to the house with freerealestates code on. It's a bit of a hassle, but if you really don't want to load the family then it should do it.