If you're on site with EHU, then you're best to use a mains type charger as per Jax's link. These provide a decent USB 5v output so are fairly universal for iPad/iPhone and other devices that might use USB connectivity for charging.
If not running with EHU, I would advise to use an adaptor to allow direct connection of a car charger to the 12v socket for charging and not to use an inverter at all. They are pretty inefficient and will cause more drain that just charging direct from the 12v.
Well, I only use Ehu when on side, therefor no probs with charging ipad etc, but I installed on the bottom of the beds near the batterie a 12volt car charger socket.
Easy to do but drilling required.
Fuse between the plug and batterie, done.
Is not that hard, but using the van batterie for charging anything up without Ehu or recharging it regularly, drains you're van batterie faster as usual.
12v sockets for cars on ebay cheap enough.
I would not advise using a inverter in this case,
I used one in a HGV lorry, and it nearly burned the ruck down using a cooling box on it.
They will get hot, either way using it.
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