My nephew is forming his first band with friends, and in place of a drummer they want software that can hold drum loops and be "played" live. I'm used to DAWs, which are way more complicated than the band would need, and which wouldn't be ideal anyway. I'd appreciate suggestions. Thanks.

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I started using recently , works on it's own or in a daw
 
akai vip , would be handy I guess.. as you can set it for a playlist
 

I use the Akai VIP, and it's a great VST host, and could be used in place of a DAW to host VST instruments for live playing, but it does not have an integrated drum or sample player.  You would still need a drum or sampler plugin for that.
 
 

You are probably looking at a hardware solution (with its own software.)  Ableton Live is a "DAW" that most live bands (big acts) use for this purpose.  The Launchkey is a hardware solution that is designed specifically for Ableton.

+1 for Ableton Live
 
Nothing is more flexible for triggering samples live.
 
When playing live, we use Live with a pair of small MIDI controllers (Keith McMillan 12-Step and QuNexus).
This allows us to stay a 4-piece, work some keyboards/samples into the show, and not have a large keyboard consuming precious stage real-estate.
 
You can setup advanced click-tracks, play virtual-instruments (seamlessly switching between advanced splits/layers), trigger samples, instantly switch songs (with tempo changes), and much more.
If you haven't already done so... watch some video of what folks are doing with Live.

+1 for Ableton Live as well.
 
Some hardware like various MIDI controllers come bundled with Ableton Live Lite, so that is a good intro to using it, and there are also numerous video tutorials available online.  If playing live is what you plan to do, there is no better way to get started!
 
Plus there are probably more hardware controllers on the market configured with Ableton support than probably anything else on the planet!

Live is very pricey for a 1st time license.

Live Intro.  $99.  That's probably all a new band needs for drum loops. 
Ableton Live Intro features: https://www.ableton.com/en/live/compare-editions/
 
You get the Drum Rack (An instrument for layering samples, synths and effects in a classic 16-pad grid), Impulse (A drum sampler with complex modulation capabilities), Simpler (An easy-to-use but powerful sampler with classic synthesis parameters), and Instrument Rack (An easy-to-use but powerful sampler with classic synthesis parameters)
 
With intro you are limited to 16 tracks and 8 scenes to work with, but that is a good start for beginners.
 
Live Lite should be the same as Intro, except for an 8 track limitation.  It is bundled for free with many MIDI controllers, such as the $129 Novation Launchpad Ableton Live Controller (8x8 backlit grid) https://www.amazon.com/Novation-Launchpad-Ableton-Controller-Backlit/dp/B00YR47GQQ
 
Ableton Live Lite features:
https://www.ableton.com/en/products/live-lite/features/