I would also expect top class lawyers to be able to write a contract that mimics the way a marriage works. Like a prenup without the actual wedding. Name change to give a family name, covering asset protection/divorce/inheritance to protect the rest of the family, most of all the children. Also, there is nothing to stop the MC giving rings to people without a traditional wedding.
Not sure who would officiate at the wedding though, perhaps Noahs mum to officiate and her boyfriend to give the bride(s) away. Yui might also be a good choice, but the problem there is that she might want to be part of the Strong family too.
I could see the MC asking Q&A to arrange this as a surprise for Tina, and then having a second arrangement with whoever is officiating to ensure that rings are available for eveyone so they could all get 'married' right after on the same day. (No need to change to wedding dresses, naked ceremony, like Star Trek.)