Having owned a wide range of fridges here are my thoughts..
go for the 63 & a slide then build a drawer next to it and a platform over the top.
This would give you additional storage above the fridge whereas if you go for the 50 you won't get that space.
Also you get a deep drawer (or 2 shallow ones) to storage the recovery gear low & kitchen gear higher which means easy access quickly if there is a need. Your swing out door gives you place to mount a drop down table so that helps.
With a little one you are carrying snacks, food for them, beverages and normal food. While a 50 would work fine you would be stacking and unstacking items alot as it is deep vs long like the 63.
Powerwise you won't see a big jump in needs between the 50 & 63 but you will like having the extra space.
Yeah this method means spending more up front but in a weekend you can build & install the rear setup and be done. Plus if you remove the fridge between trips then you can a coverage storage location for groceries, stroller and such.
Much depends on how you are setting up & using your rig...if the rear needs to be open between trips then disregard all of the above
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