I would stick with the barbells. You can handle a heavier weight with a barbell than you can with a dumbbell. Heavier weight equals more stimulii equals more potential for growth.
If you have a squat rack and a bench you can make a spot for bench, and you can (and I would recommend you do) use standing military press over the seated.
For bench, grab a bench and put it in the rack. Lower the rails on the sides of the rack so they are chest level. Rack the bar on the squat rack and then hop on the bench. If you run into trouble the bar will just hit the rails.
For Military, its easy, you can either set the rails really high and then you can just drop the bar if you get into trouble. Or if you're running into trouble before you get to a lockout, just lower the bar onto your shoulders and re-rack it. You shouldn't need a spot for this one. If you can't get away with doing standing military, you can use the rails on the squat rack and a chair or bench in the squat rack, similar to the way I described for bench.
This might piss people off if they're waiting to do squats or some shit, so be warned
If you don't have a squat rack, or one with the rails on the sides....the disregard everything I've said