I don't know the answer to your questions, but I'm answering the question you didn't ask: I want to play duets with my daughter; how do I do that?
There's a couple of interesting wrinkles.
First, you don't say where your daughter is in her violin study -- that is, how much of a beginner she is (or isn't). If she's a beginner herself, the music you're looking for won't just have to fit the range of your instrument, it's going to need to fit the smaller range of notes she knows how to play on hers (probably a much smaller set than the full range of a violin!)
Secondly, a lot of duets from the Renaissance have very different difficulty levels between the two parts [PDF]. This can be either a bug or a feature, depending on whether the two people who want to play together are similar or different in musical ability.
So what you're really looking for a specific subset of duets that can be played on recorder + violin. That is, you're looking for "that subset of duets that can be played on recorder (when I'm the recorder player) and violin (when my daughter is the violinist)." General questions about recorder and violin duets won't move you towards answers to this radically more specific question.
We can't really help with that sort of hyper-specific question here. Even if it weren't off topic, it's hard to make music recommendations in the absence of a sense of the player's skill levels. There's two parties that likely can help make specific recommendations though. The first is your daughter's violin instructor. That's the person who probably best knows your daughter's ability on the violin and can recommend music in her ability range. The second is a good sheet music store. I recommend The Early Music Workshop of New England, where most of the people who answer the phone are recorder players.
Google may also help. If your daughter is a beginner, you may find it most expedient to search on "beginner duets for recorders". She's probably got a range similar to a beginning recorder player, and beginner recorder duets may work well for you two.
As to whether there's more duets for alto or soprano, that's almost an almost irrelevant question in your project. For one thing, plenty of duets, especially from the Renaissance, don't specify instrument at all; there's plenty of 16th century music with very narrow ranges that can be played on many instruments (including both soprano and alto recorders). I think what you really want to know is whether you should trouble to learn alto.
Your options will be improved, I think, by learning alto, because:
1) Alto recorder is closer in range to the violin, which will increase the likelihood on any given piece that you'll be able to trade off who plays the lower part with your daughter/violinist. Otherwise, you may get stuck always with you playing the higher part and her playing the lower part, and that limiting your options, e.g. to only pieces that have the more complex part in the range of whichever of you is the stronger player. This particularly may be an issue if your daughter is more advanced on violin than you are on recorder, in that Renaissance duets tend to put the really boring part ("tenor") in the lower voice.
2) It's not like you'll stop knowing soprano. Wait, okay, so you will, briefly. There's a part of the process of learning alto in which one gets badly confused, and one's competence when one switches back to soprano drops. But if you persevere, then you'll have both fingerings, and be able to swap back and forth. Having an additional fingering means that you have additional options musically -- you won't have to pass by a piece in the alto range because all you know is soprano, and vice versa.
However, there's a third option to learning alto or sticking with soprano. If you like the sound of the alto better, and you already know C fingering, and you want to play duets with a violin... have you considered taking up tenor recorder? Closest in range to the violin, identically fingered to the soprano, and has an even mellower sound than an alto.