I came on the K1 visa, we had planned our big wedding for a little later, but to make sure we fulfilled the 90 day rule we first got legally married. Why don't you do that? we did everything in half a day! No appointments, nothing! We went to the county clerk to get our marriage license that we had to apply online before we went (just a quick online form) and that took 30 min max incl the waiting in line, then we went to a UPS store that has a notary (make sure to call before if a notary is in, we had to wait an hour for him to start his shift), just bring marriage license and ID's, they will just sign your paper, then we just went straight back to the county clerk with the signed certificate, they registered us and gave us the official marriage certificate right away, filed AOS a few days after. That was in Tennessee so not sure if all of this works the same for you and I know the UPS store is not very romantic, but you can always have an official ceremony and reception after.