Courthouse or outdoor park?

If it were me, I'd choose the park. You'll already be in the location for your pictures and you won't feel rushed by the clerk who will perform just the basic ceremony. You can always scout a location beforehand as well knowing you have attendees who tire easily. Coincidentally, we ended up getting married in a local park due to the craziness of last year and it was a beautiful ceremony. We did do a morning ceremony so we could take advantage of the pretty morning light, so there were only a couple people who hung out in the background watching the ceremony. I barely noticed them. We took our guests out to brunch after we finished pictures.

I would do the park. Since you're only inviting a few people, maybe you can bring a few folding chairs for them to sit down?

You're welcome! I also had a guest who wasn't able to walk far, so I had one of the other guests bring a folding chair for her so she could sit during our 20 minute ceremony. I also gave my photographers final say on the exact location of the ceremony based on where they thought would photograph best/have best lighting/etc. We had a general area picked out (based on the permit we were able to get), but they chose the exact spot. It was a beautiful experience.

Scout out areas in the park, there may be a beautiful area with a bench for your guests who will need to sit. The park would offer you that more personalized ceremony.