A lot of people who have issues with this type of thing, have an issue with lying.
You don’t need to send out announcements that you’re married or do anything else. Just when you send out invites for your party, the wording can help. “You’re invited to celebrate the marriage of ___ and mollykate92.”
You might get questions about it still though. You can also just tell your families about getting married, and word of mouth will take care of the rest.
I know a couple who got married quickly to ensure they were legally married before the birth of their child. They then had a huge celebration 1 year later. I attended both ceremonies, we gave a gift, we had a blast, and there was no side-eye. The reason it went off that way was because they were honest and never tried to mislead anyone. They exchanged rings, which they then wore, she changed her name (legally and on social media), with their legal marriage, and we all still went to her second ceremony, watched them exchange vows with her in her beautiful, white dress, and ate delicious cake.
I think it’s a little crazy to say you won’t consider yourself married, when you are married. That’s like saying you don’t consider yourself pregnant, when you actually are pregnant. Some things just are. And it’s not a bad thing or something to hide, and people are more accepting of honesty then pretend.
Of course, at the end of the day, it’s your life. However, I’ve seen this work beautifully, with full support, and large attendance at the delayed reception/celebration, and when I’ve seen it work was when it was done with complete openness and honesty. You don’t have to tell people why you’re getting married now and celebrating later. But be honest once you are married, that you are, indeed, married.