I'm writing this as a volunteer, not a client, so this will be value added if you are looking for volunteering opportunity.
These are good and very patient folks doing things better than what I could. Aside from a myriad of services they provide their clients with, which you can read about on their site, they also provide a seamless, well coordinated volunteering options for groups of varied sizes and ages.
I have volunteered with colleagues, individually, and with my kids, and it's always been easy to coordinate, organize and we've always kept busy.
The volunteer coordinator, Anthony, is organized, responsive and accommodating as can be. Expect to attend one time orientation (pre-scheduled, and one representative per group is fine), then stay in touch with coordinator for upcoming opportunities, work to schedule an event for your group or just let him know when you have a spare hour, they'll put you to work.
It's stone throw's from UNLV. Best part- you get an outside glimpse an newly restored Liberace mansion :)