Thanks for the great advise so far! We'll be staying for two days prior at the in laws in Klamath Falls. My 7 year son hasn't seen the lava tubes or the petroglyphs at the Lava Beds. I suggested to my wife we head down to the lava beds with Grandma and Grandpa on one of the days we'll be staying with them. It's not too far from their house.
I have been considering Manzanita Lake at Lassen, but wasn't sure how many days my battery can last without charging. (We'll probably dry camp both nights in the Redwoods.) I'm new to trailer camping as of a year and a half ago and we have mostly used the trailer at campgrounds with hookups so far.
The private campground I was looking at near Lassen is
Hat Creek Resort 11 miles from the park. I did a Google Search on Lassen and Bumpass Hell is at the top most every "must see" list so we'll hike that for sure:). (I noticed there's a lava tube near Manzanita Lake. Is it worth seeing?)
I do think we could spend more time at either park and have plenty to see and do, but I'm not sure how many days we can be away from home.
As far as the drive to the Redwoods, I noticed Blue Lake Casino just east of Arcata allows dry camping in their parking lot. I was thinking that might be a good place to drop off the trailer before the drive down to the Avenue of the Giants? We'd have the rest of the day to explore and then dry camp at Blue Lake Casino that night.
For the next day, I'd head north with the trailer stopping to see some sights along the way. Hopefully I'd be able to drop it off at a campground and have some daylight left to explore without the trailer in tow. The next day would be open for some exploration, but I'm not sure if I'd need to tow along the trailer or not.
Thanks again for advise and suggestions!:B