last minute camping trip recommendations

We have some time and wanted to do a last minute camping trip with our travel trailer.  Can anyone recommend a place where I don't need reservations and can take our trailer?  It's 24' long (in case campgrounds have length limitations). 

Been searching and like Shaver lake, but sounds impossible to get a site.  And we have to fax in a reservation request.  Based on a recommendation here, we went to and loved Wright's lake, but don't think they allow trailers (our size anyways).  Have read good things about Sardine, but don't know if we'll be able to get a site. 

Looking for a place close to water for swimming and fishing (doesn't have to be same water source), some light hiking.  Kids will bring their bikes and various balls to play with. 

Thanks,
Nate

Are you talking the weekend before or after the 4th of July?
You could always try Campground By The Lake in Tahoe if it's the weekend before.
Convenient location for the activities you described and they accept large trailers.

Yeah, this would be from Thursday 6/27 through July 2nd.

Seems like there is always a lot of sites available last-minute at Millerton. Lake San Antonio is first-come first-serve too (no reservations allowed/required).

What about Lake McClure/McSwain?I think McSwain is the troutlake.

There are probably spots there and they accept large campers.  The sites are close to the water, plenty of lake to padde, fish are sometimes plentiful, there's some play spaces for the kids, and it's only about 2 hours away.