The following NPS info was found on the net and helped me make my decision. Like you we camp a lot in Forest Service and NP camp grounds.
"The National Park Service (NPS) noise limit is 60 db at 50' from the source. This restriction is not well published, and not easy to find on the internet. I think it applies to off-road vehicles (snow mobiles, ATVs, etc.) as well as generators.
for a discussion and an on-line calculator for calculating noise levels at different distances. As a rule of thumb, the noise level drops 6 db every time the distance from the source is doubled."
So, first decide on how much generator you need. Lights and recharge the batteries, 1000w will do the trick nicely and the inverter types will easily meet the noise restrictions.
Want to run the AC and or microwave etc you'll want a 3000w unit or a couple of 2000w units coupled together. Again, the inverter or "suitcase" type units will do the job well.
I decided on the Dometic 3000w unit since we wanted to be able to run the A/C. Nice package, runs as quiet as the major brands and 1/2 the cost. Used it several times this past season in both modes. It has an "Econo" switch for the minimal load and can run up to 30amp for the A/C. Support from Dometic has been great and has definitely earned my recommendation.