Second, make sure you piece together detailed instructions to every natural hot pot you can get to during your trip. Period.
Third, don't try the cured shark, but do try the famous hot dogs (from the hot dog stand Bill Clinton ate at nonetheless), the whale and the puffin (I know, kinda sad). And, eat at Narfeyrarstofa in Stykkisholmur (get used to these types of words too -- they are everywhere) and get some sort of fish. Also make your way down the cobble-lined streets of downtown Reykjavik to Bernhoftsbakari -- the oldest bakery in Iceland; do not, however, order everything that looks tasty to you because you will not have enough room in your stomach, and you will be sad.
Fourth, splurge on a lopapeysa for both you and your husband because 1. they are the warmest sweaters on earth and 2. they are hand-knit by sweet little Icelandic women. But, don't buy them in a store in the heart of downtown or at a tourist attraction (and certainly not at Geysir) or you will surely get ripped off. Try instead at the Kolaportio flea market (which provided our golden finds) or somewhere else that sells them for less than 15,000 krona.
Fifth, hike to Smoke Valley and Seljavellir; you won't regret it. By far they will be two of your most favorite outdoor swimming places, and they will both provide you with magical experiences while tucked away in the canyons of Iceland. Also, the Blue Lagoon; it goes without saying, and even though it's a bit pricey, the water color and free face silica will quickly make you realize it was worth it.
Sixth, joke incessantly about how 500 krona sounds like a load of money even though it is only $4 US.
Seventh, you will soon realize that Iceland -- at least at the end of September -- is the land of waterfalls and rainbows. Prepare yourself to see at least one rainbow and five waterfalls each day without even trying. But, on purpose, you must travel to see Gullfoss, Seljalandsfoss and Skogafoss. Make sure you climb on precarious rock perches and up steep muddy embankments while you are at it -- it will make your experiences compoundingly more memorable.
Eighth, plan to travel south to Vik to visit the black sand beach there and see the basalt columns and basalt cave in this Jonsi video (note to people I may have misinformed, I was once told basalt columns are quite rare in the world, but it turns out they are all over the place). You will also want to relish on this beach for a little while because you will find it entirely too enchanting to want to leave quickly, despite chilly winds and low temperatures.
Ninth, be sure you thoroughly acquaint yourself with the speed limits at all times on Iceland roads because speeding tickets in Iceland can cost upwards of $1,000. However, you may be lucky and squeak away with only paying $375 after the nice officer gives you a $150 discount for paying on the spot.
And tenth, book at least 10 days for your trip because 5 and a half days simply isn't enough. Also, don't watch the Icelandic film Volcano on the plane home because you will cry THE ENTIRE MOVIE since it happens to be the saddest movie ever to be fimled.