I will travel to a conference at which I will present my work. My funder usually reimburses me for fees of conference registration, travel, and accommodation.
However, since my wife and kids will accompany me, I will book separate travel tickets for them, and a family room, which is usually more expensive than a single one.
I will ask the funder whether/how they would reimburse me for the accommodation.
I guess many other academics around the world travel for work with their partners, friends, or families, and I am wondering how they usually/ideally get fair reimbursement for accommodation shared with other non-funded travellers.
Usually, you will explain the specifics of your travel and provide some documentation about
- the actual expenses for travelling with your family
- the expenses you would have had, had you travelled alone
You should then be able to make a case for getting reimbursed for the (lower) expenses listed in item #2, even though all your bills show the (higher) expenses from item #1.
If there was anything that cost the same, or even less, for the whole family compared to what you would have paid alone, make sure to provide good proof of the hypothetical 1-person-price and you might even get reimbursed some of what was used by the entire family :)