For pinholes, latex sealant seems to work really well for me. I've pumped a couple of dozen mL of Stan's into my son's tubes and that seemed to have addressed his propensity to run over goat heads.

For patch kits, I like the ones Rivendell sell better than even the Rema ones, because the Rivendell patches are extra thin. However, if you're not ordering other stuff from them, the Rema kits makes the most sense as you can pick those up at any bicycle shop. And yes, it's worth it since it's <$1 per patch and you can do it in a batch for efficiency.