Chest Freezer in the garage

Definitely invest in the freezer alarm. I found out the hard way and lost half a freezer of meat a few years back. Alarms are cheap and work well.

Yeah, an alarm is the way to go, if you plug them all in and the breaker doesn't trip immediately.

After all, I would THINK it would be rare that they would all start simultaneously. Driveway test them, together, for a few days and return your new purchase if it turns out to be incompatible with the others.

One thing to consider: Having all these appliances will heat up your rig quite a lot. Depending on where/when you camp, this can be a good thing or a bad thing. I sure appreciated the heat my one freezer gives off this fall. But in summer...

If you have a 15 or 20 amp breaker then the amperage at peak (usually start up) of the devices can't exceed that. Some where on each device should list the AMP draw. I looked online and couldn't find an example for a chest freezer for you though.

I'd also get a power outage alarm, you can find several on amazon.