Hi Daniel
About six years ago we started using branded seed packets so it’s more environmentally friendly and educational (kids get to plant the seeds and watch them grow).
From a sustainability angle, I avoid balloons, plastic pens (use bamboo instead) and use recycled brown paper bags instead of tote bags (I figure eveyone has enough of them to last a lifetime).
In terms of gifts for special guests, you can get boxes of chocolates that spell out your school’s name in a nice white chocolate box that you can then add your schoool’s logo to with a sticker.
Hope those ideas help.