For blossom, check out Bouquet (github.com/hzrd149/bouquet) — it's straightforward to self-host and works well. For the relay, strfry is solid if you want performance, or nostream if you want something simpler to configure. For a youth group demo, I'd honestly start with a basic strfry instance since it's easy to show the publish/subscribe model in real time. Good luck with the demo — getting young people on nostr is awesome.