I'm not very experienced with cranes, but the yellow 20' round slings (6400lbs each I think) and 12' slings with 3/4" Crosby shackles work very well and are versitile. 2 eacg. Actually.... I think you recommended those to me. Most importantly, pretty inexpensive. At about $60-$75 each. Double them up for stability. But you know all this. I got mine at Holland.
Remember, sometimes you'll have inexperienced and shitty climbers on your hook, keeping things simple and inexpensive might be the best. Maybe even wire chokers cause that's what people are used to dealing with. I'm not sure I'd hand someone who hasn't done spider legs the rope setup. Hope that can help.