Hi Derek,
Welcome to the Moms Panel! This is a very common question - and I am a firm believer that it is not necessarily what you wear, but how you wear it. You dressed in nice pressed shorts, collared shirt, belt could look much nicer than the person that wears wrinkled trousers and an untucked shirt although the latter would technically adhere to the
recommended guidelines. So I can tell you that you will not be turned away from your meal for wearing what you described but there are passengers out there that may give you a sideways look for your non-conformance (I'm not one of them).
I would probably draw the line at the "dress up" night, and suggest bringing slacks for that evening, but again it is your vacation - as long as you are dressed respectfully I think you should be comfortable. I will caution that if you have booked a meal at Palo, shorts are not permitted and you will be asked to change.
I hope this helps, happy packing!