Okay, I don't doubt the unwed/unchild people might not have good ideas, but at some point it feels a bit like asking your priest for wedding night techniques~ perhaps well read, but nil practiced.
1) with the kid and staying at home~ from YOU she wants help with all the new things: diapers, late nights, feeding when you are physically able, and PERMISSION to go out, alone to shop/friends/groceries/whatever, which means you say, "Hey baby, why don't you figure out a couple hours today that work for YOU to go out and I'll cover junior". This is not a gift, because she expects it.... and the salon/spa thing can be a pain in the ass unless you are coming in as wing man.....
2) You be a family now~ mama bears, and not all are, but mama bears tend to want to know how it affects the family. So, maybe alone time is nice, but not as nice as you buying snowshoes for her and you, AND carry/sled cover thing for the kid to come with. Now a Saturday afternoon becomes family adventure time and you thought through the details... which is the "unexpected" gift.
3) Why guess? Set her down and say, "hey baby, our lives have changed, I've got all these ideas and assumptions, and figured doing a big surprise that doesn't work will cost twice as much...." then get info on what makes her happy and plan a X-mas shopping trip together. for the tree, get some little things~ and if she likes "nicer", but doesn't buy it, don't be afraid to get a gift card. Victoria's Secret apparently makes functional things women like, who knew? I don't think you do either.
4) What she needs from you and what she wants are very, very different~ assuming you're not a complete goomba, getting a spa day away so she can come back to half-day of things not getting done might backfire.
5) Incorporate her friend~ sorry, this likely doesn't include you. See if you can get a two fer deal so she can take a friend/sister/mom. An hour massage alone might be heaven, 6 hours at the spa chatting with the nail/waxing/hair cutting gals, with nowhere to go but home afterward, might not be that thrilling.
6) take up some workout classes WITH her~ depending on your/her gym. Stay away from the Zumba, that's just ass kissing, and you can't love someone that kisses your ass, but what about kick boxing or similar cardio strength that uses weights. Honestly, Yoga is freakin' awesome if you can get into a decent mixed class and you're not the only dude. LifeTime Fitness FAMILY membership can be a godsend. She can do a class, you go free weights, meet up in an hour at the hot tub, shower, grab a smoothie at the cafe and chat, get kid~ a two hour date with sitter built in.
In the end, I don't know Jack. But can't help but think if you are asking a bunch of duck hunters on a web site what is up, your strategy might be flawed. Of course, the only thing I can guess is she is a saint and you out kicked coverage on her looks, so you might not really have to worry