Yes its do able, just get another Contract Sim Only Plan put on your Family Account, so your end up with 3 Numbers, You (UL Data), your Wife and the new Sim for a Dongle, Router MiFi etc.
As you probably already know, the Gifting Allowance for UL Data Plan will be either 100gb or 120gb depending on the Plan, so you would need to share this allowance between your Wife and the New Sim.
Again you already may know this, but Gift your UL Data Allowance on the 1st Day of your Monthly Refresh Data, otherwise your UL Data Sim will start to eat into the Gifting allowance.
Just to note, using Mobile Data on Routers, MiFi's can eat a load of Data, especially if you plan to Stream or Download Films etc in the Caravan, so you may want to consider this before committing to another Contract Sim and the type of Data Allowance that comes with it, try it first with your UL Data Sim, then do the Maths.
All of the Above is subject to EE's FUP's.
