35mm or 50mm for full body portraits for Nikon DX camera?

Shooting full bodies with "satisfactory" bokeh is not easy. The diameter of your background blur is f/a where a is your aperture number. With full bodies filling the frame, you probably want bokeh circles for distant background that are at least 30mm in comparison to the body and/or facial features. Which is about 50mm/1.6. Shooting with 50mm on a DX sensor is possible, but you'll have to place your subjects at considerable distance to get them full-body, and the background at considerably more distance to give it sufficient blur. That can be difficult.

Full body shots with bokeh are more or less the quintessential use case for "full-frame with prime lens". You can labor around it a bit, but that requires lots of space for getting your scene set up and makes your subjects appear a bit flatter than if you work with an FX setup.

Things to consider…

35mm in a DX body will let you take full body shots from reasonably close.
This will, however, give you 'short legs syndrome' if you're not careful. Shooting from any lower than chest height to try balance the leg length starts to get a bit 'up the nose'. Your bokeh will be harder to achieve on a relatively wide lens, even with the aperture wide open.

50mm will let you step back a bit, but you are now probably in 'must do this outdoors' territory in order to get sufficient distance between you, your subject & your background.

You can test both these ideas out first using your kit lens, just to see how the framing & leg length works, if not the bokeh.
Late edit I just realised you said 'two kit lenses', my bad - so you should be able to test this at all lengths & then know what you need for framing.
Add to that that your bokeh will get 'bigger' on a longer lens, so long as you can achieve the necessary distances.

Stepping up to an 85mm [or even longer] will improve your bokeh still further, and completely fix 'short legs', but you now need even more space to work in.
I'd be inclined to rent or borrow an 85mm, or 105mm or even a fast 70-200mm zoom before finally choosing which you need, or have space to use.
Personally, I tend to go for the longest lens I have room to step back for, for anything I need to separate subject from high blur background.

I guess one additional constraint might be budget. You can get a 35mm 1.8 for just over $£€ 100 if you shop carefully [it's nice enough but it's not a bokeh king, by a long shot], but the 1.4s go up in price pretty sharply - $£€ 400 for the 50mm up to $£€ 1,400 for the 85mm & nearly 2 grand for the 105mm.

50mm and back up a few feet. F4. Make sure your subjects have plenty of space behind them. Focus on the eyes or none of it will matter. Don't focus anywhere else.