Reddit mentions of Visual Rainmaker

Mostly just wanted to say good for you. I don't think you can go too wrong here, especially if this is your first time giving her a dedicated day. I guarantee she will appreciate it, no matter what.

I would second most of what the others have already said: get her some cute and decently made diapers, give her a few bottles (add a little sugar/sweetner to the milk and warm it a little to make it extra wonderful). I'd recommend getting a bottle with an adult sized nipple (it can be a little difficult with the baby ones), too. Prepare her food for her and maybe feed her, depending on how little she is. I actually like baby food, myself - you might make her try some (something fruity - not veggies/meats), but sounds like your wife might be a little older than me, so maybe mac & cheese, chicken nuggets, and hot dogs might be in order. Maybe make her wear a bib, depending on her age.

I think cuddling is one of the most important things - spend lots of time cuddling her and holding her. I also second the kisses on the forehead. Tell her you love her just the way she is, and use whatever little pet names you have for her (or princess or sweet pea if you haven't given her one yet). If you're big enough/she's small enough, maybe carry her some.

Watch some Disney for sure, but also be sure to read her some cute/fun bedtime stories when you put her down. Then put on music box-esque lullaby music softly (search lullabies on YouTube).

I'd caution you on the spanking(s) - some people love that but others don't - you should know or ask your wife about that, don't assume.

Lots of folks like pats on the butt now and again to be reminded of their diapers. You should definitely make a deal about checking her diaper (fingers in the elastic to see if she's wet).

If she doesn't have an adult sized pacifier, get her one (but it sounds like she might). Likewise, she probably has a favorite stuffie, but if not, get her one. I also wouldn't go get furniture to start, but a cute snap-crotch onesie and/or footie pajamas would be great.

I also highly recommend toys. I love my visual rainmaker (https://www.amazon.com/MP400-Visual-Rainmaker/dp/B0018YYPJ4) and my Perplexus Epic. I can really play with those for a good while and feel like a baby, moreso than some baby toys. As others have said, coloring is also always good, as is Play Doh.

Try to enjoy her happiness and enter into the pretend with her as best you can. The straighter you can play it that's she's really little, the better. Whatever you do though, it will be great!