This depends on how often you run the van. You should be able to charge phones several times a day and even supply constant power during the day to phones without issue so long as you run a meaningful amount of time occasionally.
A power system similar to an rv would be great and all you need is a battery and an isolator. You could simply upgrade the starting battery and be fine. As long as you are already using the van as transport daily and your charging and battery system are good, phones and a smoothie should be ok.
There are automatic switches for load control that disconnect power to protect reserve power for starting rv/marine/utility.
All of these tacts would easily take solar input, it just depends on if you want power independent of the van at base-camp or if the van is base-camp and stays put like a parked rv with run-about/other vehicle.
No doubt a pv panel is probably the best solution for long term power provision. As an appliance/equipment investment in your homestead, its hard to beat and will likely outlast all but durable tools and the best buildings.
For $300-$500 you could have a 340 or so watt system; battery, control, panel, mount, wire, fuses, made of good parts. Even less of you simply add 50 or 100 watts solar and a controller to your van.
https://www.altestore.com/store/solar-panels/solarworld-290-watt-solar-panel-sunmodule-sw290-mono-black-frame-p40718/
Solarworld modules are among the best devices of their type ever made.
https://www.altestore.com/store/solar-panels/trina-solar-multicrystalline-solar-panels-p40874/#TRI255PD0508255
You can get 100w and smaller for about the same money, so if budget and mounting location allows, 150w-250w is the smallest at a cost effective price. Most any simple pwm charge controller will handle either of these panels and the battery will be ok if your controller is sized to not exceed max amps charge.
Trucker and rv-marine appliance suppliers and even truck stops have DC appliances of all sorts, and smoothie blenders are popular, so unless you are loyal to your nutri-bullet or need ac power for other loads, you could easily get by with no inverter.
The vortex blenders are great! I even used ours to grind
coffee in a pinch. Pretty rough job and hard on the blender, but it worked. When im lazy or its a big job, i chuck my cordless drill motor onto the crank drive of the vortex. It will smoke a bit.... but it survived! Kidding, no smoke. I stop when i smell warm gear lube.