I usually work with Nikon, not being that in the Canon world, i would probably recomend the Canon Flash Speedlite 270EX, small, portable end robably will suit your needs for the family and house about photos. if you need something more powerfull you can always go with the Speedlite 430EX II, although this will have a less intuitive use and more complex settings to be fiddled with.. i would recomend the 270. that's sticking to the Canon Brand.
for the memory card, the most important is to use a fast card! for HD recording it has to be above 5.5mbps writing speed, otherwise you'll just fill up the buffer and be cursing yourself lol
I recomend the SanDisk Extreme 8G SDHC card which can record 24 min of 1080p video. you can buy two or a 16Gb. if it's to expensive you can look to the Sandisk Ultra range aswell, altough it will be slower when downloading it to the Laptop.

Sorry for the long off-topic answer and my poor english, in a couple of months when i move to the Uk hopefully it will get better  http://paulomartinsphotography.tumblr.com

Thanks for that,and there's nothing wrong with your english

Anytime mate

anything else i can help you with just send me an mp http://paulomartinsphotography.tumblr.com