Outdoors the Canon IR/ST-E2 system is too easy to upset/misfire/no fire, I would not move forwards with that as an important component. Radio based triggering systems vastly outperform all optical triggering systems outside.
If an AF assist light is a key feature then the Yongnuo YN-622C-TX and 622 receivers look a good way to grow your 430 based starting kit. Obviously price is always a concern for this stuff but I would strongly caution against going the seemingly "cheap" route, really work out where you want to grow to and use that as a guide.
If an AF assist light is not, in the end analysis, critical, then a set of the Yongnuo RF-603 is a very highly specced cheap dumb tranciever. I own the earlier 602's and have never had an issue with them for simple manual triggering.
Of course you could, as they are so cheap, combine your first idea (the ST-E2 AF assist) with the RF-603, they have a pass through, you need to check compatibility but you might be able to mount the ST-E2 on top of a hotshoe mounted RF-603 and then have a 603 for each flash, that way the reliable radio triggers will fire all your flashes, the ST-E2 covers your AF assist, all for very reasonable money. Golden.