I would like to concur with the notion of nice khakis and a long-sleeved button down. As chilly as it’s been lately, you shouldn’t be warm. You’re mistaken though that a tie must be worn with a jacket. Ties are optional these days, and a nice long sleeved shirt can stand on its own.
As others have said, short-sleeved button downs are unacceptable. And yes, if not new underwear, at least wear nice ones.
I was watching an old Tonight Show clip last night, and almost fell off the bed. Carson’s lapels just about touched his “shoulder-mah-pads”! So I jumped up, opened my closet, got my blue blazer out and measured the lapel width. The lapels are 4" at their widest.
Would one of you guys who maybe just bought a sport jacket measure yours and tell me if this is acceptable?
Am I obsessing? 
Thanks!
Quasi
Well, a blazer is worth obsessing over. Every grown-up guy ought to jave a good one. [steels herself for the onslaught of people about to call her a bourgeois snot]
I agree with the others–a trip to a good mens’s store is in order. Bring the jacket with you if you want. They can tell you if it is laughably out of style. And if it is still good, then you can try it on with whatever clothes you are thinking of buying.
<Andy Sipowitz voice>
What’s wrong with short sleeves?
</Andy Sipowitz voice>
I hate long sleeves. What good does it do to look good if you feel bad?
…may indeed look good on some guys, Booker, but I’m not one of them (unless it’s a T-shirt). When I put on a short-sleeve dress shirt, I look like I’m trying to sell you something.
Quasi
On a first date, it’s better to look good than feel comfy. It would be nice if you could do both, but if you have to choose, go with stylin’. And, please don’t say that if the person is going to like you, they’d better like you short sleeves and all. There’s time for that, but not if you don’t get past the first date. I’m telling you, people are just looking for a reason to be the first one to reject (it’s a defense mechanism), so why make it easy for them?
Short-sleeve shirts are fine.
Short-sleeve dress shirts make you look like Milton Waddams.
Sue Duhnym -
You are a Goddess… I could not agree more with your suggestions and bravo on Faconnable! We need to go shopping together - for me!
For everyone else -
For added emphasis - NEVER EVER wear short sleeve dress shirts. Don’t buy them, stop yourself from trying to rationalize wearing them, burn any you own. You are not 12 any-more being dressed by mommy for Easter church services. 
Long sleeves are not THAT uncomfortable.
Finally - shoes, pants, button down dress shirt, jacket, etc., are great starts but to REALLY separate yourself from the herd and to impress it is ALL IN THE FINISHING TOUCHES. Appropriate watch for the attire (there is no such thing as a single watch that can be worn with EVERYTHING), distinctive wallet (remove 10 weeks of receipts and 14 credit cards before the date!), designer socks and belt that compliment the attire.
MeanJoe
MeanJoe
Ascot?
Y’all are the greatest, and thanks again for your advice. Y’all don’t, but people who do know me, don’t see me as going to a haberdashery (or however you spell that) for my clothes and to tell ya the truth, I’m a little reluctant to go myself.
Not that I don’t wanna look good, but because it doesn’t go with the Quasi personality. I took the best of your suggestions and called in an order to Land’s End last night.
The blazer will pass muster, and it looks like I’m all set except for the shoes, and I’ve settled on a pair of brown “docksider”- style loafers with a brown belt.
The guy at Land’s End says to run the pants through a gentle wash cycle to get the “new” smell out.
So I will keep my eye on this thread in case y’all have any more advice, but as far as I can see, I’m ready. Still don’t know what she’s gonna wear, but I’m pretty sure that unless it’s an evening gown, we won’t clash.
Thanks
Quasi