Good luck WBF - that's great news. It will be interesting if you love playing mixed with each other or hate it!!
From my experience the mixed doubles tournaments on the USTA website are very poorly attended and are often cancelled through lack of entry - unless they are very high standard. Even then the national over 30's mixed had just 3 couples this year.
It's worth looking for smaller local tournaments at the local racquet clubs which will not be on the website but will often have better draws.