Uranyl acetate is said to be ~10% w/v solubility at room temperature. Aim for this, at least, or even 15% if you're warm! Say 7 g in 50 ml. water.
(A drop or two of acetic acid may help, if it tends to deposit solid basic salt due to hydrolysis.)
You can expect a bright green fluorescence when you put it under the UV! Exposures will be lengthy.
I don't know if you can mix it with your ferricyanide solution, before coating, without it reacting - it's worth a try. Otherwise develop your Uranotype in ferricyanide as usual.
P.S. If you have any sodium tetrachloroaurate dihydrate, NaAuCl4.2H2O, dissolve 1 g in 10 ml. Mix this solution 1:1 with your uranyl acetate solution to make a nice gold print - uranochrysotype!