If it were me I'd have the pull up bar attachments on the power rack and a removable dip station (Rogue Matador). Get the rack that has added weight storage. A good bar for each rack. Get 2 benches for the racks, the adjustable ones with wheels that can be moved in and out of the rack and used at the dumbbell station. More people are going to benching in those racks than squatting anyway (I know, shocking, right?). The weight storage on the racks will free up some space, no need for barbell storage as all bars can stay with its respective rack/platform.
2 power racks with weight storage- add pull up bars and dip stations to it.
Each rack needs a bar, a bench, & 300 lbs plates (minimum).
2 deadlift platforms- 2 deadlift bars, 2 deadlift jacks, 600 lbs plates (minimum). I would build my own to save money out of plywood and horse stall mats, have weight tree between the platforms for shared weight.
That's great advice right there!
I think this would be a good start to a gym and will probably won't exhaust your budget. You can always add things later, incorporating some input of the people who will be using the equipment. Remember this: buy nice or buy twice!