Need help choosing Greek/Roman authors

[Rev. Rye]

Cicero - Would prefer to read his letters, not so much his treatise on rhetoric. What's "An Old Age," as Rev. Rye suggested, about? What's a good translation (for either/both)?
Catullus - Natachan said he was fun. What specifically?
Seneca - I'm on the fence. I don't want to get too distracted by non-philosophers during this run I'm on. What would you recommend, specifically? And trans?

Cicero: On Old Age is a treatise on aging. One of my Latin teachers listed it as her all-time favourite book. That said, I don't know enough about most specific translations for most ancient authors (The Stoics excepted) to recommend a specific translation; this is compounded by the fact that, for whatever reason neither Oxford nor Penguin have complete translations, so I'll recommend the Loeb Classical edition.
Catullus: His collected works (in a bilingual edition with both the original Latin and English) are about 150 pages, not including notes. I remember accidentally mentioning Poem 16 in class, and the next day, most of the students came in, shaken by what they read in their spare time.
Seneca: Letters to a Young Stoic, Penguin Classics Edition. Boom.