Sounds like a good plan to fill your needs.
Again, you might check in with the peeps at popupportal.com about reliability of the Parallax unit. I read one posting but that seemed to be mostly about installation wiring confusion.
But,,, not to be accused of beating a dead horse. If you get a power center with a 3 stage charger now, if you want to add a battery
in the future, the three stage charger can be left on 24/7/365 and it will take care of your battery
all winter long for not all that much power consumption.
Good luck with your project.