Given your situation, I think it would be ok to have two ceremonies. I (Canadian) got married to my husband (American) at city hall and we planned on having a reception/celebration with everyone who couldn't be there, but it hasn't happened yet... if you already have a "second" event planned, that's much less work for you already. If you wanted, the second ceremony could just be a reception (but still a great celebration).
It's ok to not have the second ceremony and make the best of your courthouse wedding. My city hall wedding was charming and intimate. Wouldn't change it for a thing.
And it's ok not to get married on your desired date. My SO and I always envisioned we'd get married on our dating anniversary, which is right the middle of summer. We ended up getting married in the middle of winter so I could apply for change of status before I graduated college. And I love our new date! I actually forgot all about our dating anniversary this year. The new date will become more important to you pretty fast.
Would Georgian civil ceremonies involve religion/god at all? I got married at a city hall and there was no mention of god. But I'm in a not-so-religious state so maybe that's why. But you could always try to find out in advance what the vows would be like, and find out if they allow you to say your own vows.
As for the courthouses, is this one anywhere near you? It came up when I googled Gwinnett courthouse. What a gorgeous building. You can still do outdoors pictures in the winter. I don't know if Georgia gets that much snow, but it'd look really pretty with snow on the ground. And even if there's no snow, a great photographer can make up for a not-so-great location.
What it comes down to is doing what you (and your SO) want but also what would make the most sense in your situation. Make a pros and cons list. Immigration and money sucks. I had a 4 month summer vacation this year because I was waiting on my application. It wasn't as fun as it sounds, trust me. I wish I could have started working months earlier. If you will need money, an earlier wedding may be the best option. But if your SO will be able to support you while you don't work, you could consider keeping the April date.
Best of luck!
