This is something I would judge by how well you know the family, and what's going to be easier for your wife. If she knows that the only way for her to be comfortable is to wear the capri's, then by all means, wear them. I am of course 7mo. pregnant, so I might be thinking a little off kilter then most would
But funerals aren't any reason to make yourself faint, sick or any other kind of reaction she may have. Wear what feels right, stay cool, and don't be afraid to as to go sit down if you aren't feeling well.