Activitates Pro Liberis (Ascanius.org) combination of art, culture, history, Latin, Greek, games etc. Also the materials cover a wide range of ages (about 1st-5th), so can pick and choose what works for your students. Tons of already prepared worksheets, picture cards, games. Invaluable.
Latin is Fun, John Traupman, Great pictures and cartoons, great intro to grammar, grouped into topics like family, school, etc. The grammar can get challenging – It would work better for 5th than 3rd.
First Latin, Marion Polski. Combo of history/culture and very basic grammar and vocab and derivatives.
Tres Coumnae Latin stories by Justin Schwamm, designed to be engaging and interesting for upper-elementary-aged children
Charleston Latin by Frank Morris, and elementary school curriculum.
The Big Book of Lively Latin, by Catherine Drown, an elementary school Latin curriculum.
Latin Memory Songs (Rainbow Resource Center)
Latin Alphabet Songs (Latinteach)
Pronouns and Question Words David Pellegrino’s Latin mnemonics songs (Latinteach)
Latin in Harry Potter (Magistra G.)
Latin Songs (Magistra G.)
Animals in Latin (Magistra G.) with pictures
The Iris Project Annual. 60 page glossy magazine, with full colour throughout. It features several articles by expert classicists as well as pieces on The Iris Project’s work in schools, other outreach initiatives, a mix of light pieces, competitions, news, reviews, games and lesson ideas.