That was going to be my suggestion.
Too extravagant? After she blows out the candle, cut the cupcake in half.
Mine too. I was once in this exact situation, from the other side, and this is what my date did for me. I thought it was a perfect way to handle it. A nice, light-hearted gesture that acknowledged the birthday but didn’t add any pressure to the situation.
Personally, I would not go with the flowers or balloons. If you give someone flowers or balloons then they have to carry them around everywhere during the date, which gets annoying easily (especially with balloons). I’d get a card and write “Happy Birthday! I had a great time today with you” inside. Give it to her at the end of the date with the, “Oh! I almost forgot!” thing mentioned above. You’ll be golden.
ETA: And, of course, if you don’t have a great time with her on the date, throw the card in a gutter somewhere.
If she drinks wine:
Bottle of wine. Small bow on it. At end of date.
Period.
At this point, if you want the restaurant to bring out anything with a candle on it, I suggest that you buy the candles in advance, and drop them off. At any of the restaurants that I worked for, they never had candles, even the high end ones.
Best wishes,
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Yes! Flowers need upkeep. Balloons attract attention; great if you’re 8 years old.
A card or the fridge magnet mentioned earlier would make better light-hearted gestures.
Agree with the other posters. Something small that doesn’t imply anything, but acknowledges the occasion. At least a card, at most I’d say a birthday balloon or a modest flower bouquet. I’d go with flowers over a balloon. 
As far a whipping something out at the end of the date, whatever it is has to fit in my pants.
What?
I’m not wearing a jacket and I’m not showing up in a car. If it can’t fit in my pants pocket, I’m going to be carrying it in my hand. We’re meeting in a lobby and walking to the place.
Fourthed.
You know, in all of those e-mails, she hasn’t shared all that much. She likes Provincetown (and the gays), but it’s not like I can just hop over there and get her a fridge magnet. She loves Bear Week there, but I really don’t want to associate myself with anything gay (other than I’m tolerant). She says she likes seafood, but only because I asked her if she does.
The place we’re going doesn’t seem to have desserts, so there’s nothing for me to stick a candle in.
I think I might just have to go with covering the check and giving her best wishes.
My first date with my now ex-husband was on his birthday. He was making me dinner at his place and he worked for a wholesale florist. I didn’t drink at the time.
So flowers and wine were out of the question.
Instead, I found a generic birthday card that said “Happy Birthday (inside) to you!” and just put “thank you for letting me share in your special day!” on the inside.
Since he was making me dinner - I showed up with a coffee cake. It was a cake on his birthday, but it wasn’t a birthday cake.
In his own words, “The woman brought me food - how could I not love her?” and since we got married – I could say it had positive results.
That being said - I really think the card idea is the best. And maybe a small refrigerator magnet of a lobster since she loves seafood? If it works out - you can always quote Phoebe from Friends later. “She’s his lobster!” (something she used to say about Ross and Rachel to prove that they are meant to be).
I second this. You just met her Friday so lunch is plenty.
That would also be a nicely humorous way to deflect if she did seem to think it was too much.
But don’t do what I did once: I happened to have some Silly putty we had recently bought in the car. Since I like silly gifts like that, I tried to give it to a woman. She wound up giving it back to me, and getting a ride home.
Just pop the candle in her entree.
Quitter.
I think you should get her something small and non-pressuring. Otherwise you’ll hear about it a year later. (I met my current GF right before her birthday and didn’t get her anything.)
If things work out, I can always get her a belated present a month from now. And I could honestly claim that I didn’t know her very well on our first date.
Go by the grocery store and get a small flower in a pot. (Cut stems will wilt before lunch is done, and she’ll be tense about how to care for them.) You know, like one of those tiny violets or something small.
And a card - why all the stress over a simple card? “Happy Birthday” is not “As You Wish.”
I wouldn’t do the dessert and candle thing, unless she endorses it. (Leaning a little forward with a mischievous look - “shall I tell them it’s your Birthday?!?”) Some people like that, others are horrified. Once you make it obvious, you’ll have no control over what the restaurant staff have to do (sing? clap? depends upon their policy) but you will get blamed for it.
Good Luck! 
Agreed. If you’re eating at a sit-down place, a note to the waiter / host saying “it’s her birthday” will usually yield a couple of staff members singing Happy Birthday + a slice of cake. Not too over the top from your end, and it’ll ad a note of fun to the meal.
Oh God - the thought of the restaurant having the waiters sing Happy Birthday to me on a casual meet-and-greet lunch on my birthday would make me want to run out of the restaurant. She might like it, or she might be like me - I wouldn’t chance it.
The fact that she brought it up in the first place suggests that she might like it. But I’m still a little loathe to try it. I guess I could try to get a feel for how she might react during the meal.