Cajons are great.
Get the version with snares, and it's basically the same as a kick and snare of a drumkit.
Zero setup time, easy to learn and play, and as Gordon said, you can stash shakers and brushes inside. Not too loud when played in a small room, they can fill a large church without a mike, throw a mike on it and EQ a bit and you can get an impressively big sound. Bring it outdoors for a quick jam session.
When I bought mine, I brought it home and had my son try it out for a couple minutes. Then off to church, and he was playing like a champ. I should note he'd been playing on the back of pews for years before that.

I have a cymbal and a small hi-hat for it, but most of the time just play the cajon, as it's all that's really needed. I've even got a kick pedal, which is a pain to set up so it never gets used - although I'm tempted to use it when I have to choose between cajon or bass

.
I've tried out electric drums, full-size kits, and even kid size kits. They've all gone the wayside, because the cajon is
so much more convenient.
Plus, it's functional as a chair - just don't use it as a stepstool!