Are there any camp sites that allow for two tents?

You could put two or three tents up at most sites, the official limit is two vehicles

Yes two tents are okay. There is a limit on how many people will be there. Not sure of the number

Many sites are large enough. We had site 63 and it could easily accommodate 2 tents.

Many sites are able to accommodate 2 tents. We were in site 82 and it was on a large uncomfortable slope, but it accommodated both the REI Kingdom 8 and Base Camp 6. Sites in the upper section are flatter, and if you have smaller tents than my behemoths, you should be fine.

It's your choice you can have as many as you want