IMHO, heavy weights (e.g. three sets of 5, 30 seconds to a minute between sets, with you not able to do the last one until later) are great for building strength and muscle, but you have to work up to it. Otherwise it's a recipe for injury.This is obviously better than nothing, but I believe heavy weights would be more beneficial, especially for older people.
I suggest, if you're new to weights go for three sets of 10 to 12 and do the motions correctly, upping the weight and downing the reps to 10 when you can do the the 36th one. Do that for six months, then change up the reps so they go between 5 and 10 adding weight when you can do the 30th.