"Będzie wy żenicie się mnie?"
Completely wrong ; )
"Czy wyjdziesz za mnie?" is the name of the game.. "wy" - is plural it would reassamble asking multiple people at once about marriage..
Another thing is that in Polish you have two words for getting married one for men one for women, the one you used "żenić" is for men which is incorrect in this case. "Wychodzić za mąż" is the women version ; )