Yep, I'd go pants and shirt for both of you. I wouldn't do a dressy top - you're not going out for dinner. Absolutely nothing sparkly.

I'd get DH some dark chino type pants that he'd wear out to dinner and a short sleeve shirt.

Honestly, I don't think that would be overdressed. It's not like you're turning up in a suit.

I wouldn't wear denim unless I was going for an interview in a jeans shop.