We ride wheels that are probably heavier than we need for about 98% of our riding, but they've been 100% reliable for about 7,500 miles so far.
Talk to an experienced builder of tandem wheels & add spoke count and anticipated speeds / road conditions into account while making your evaluation.
A quick search of one retail site finds some of the rims mentioned above could be available in ranges of spoke counts from 32 to 48 depending on diameter.