It is certainly right to charge a pet fee if your guests bring with them pets in your vacation home. Pet owners recognise and accept the fact that they ought to pay boarding fees for their pets.
Accepting pets at your vacation home means adding convenience and enjoyment for your guests. Expectedly, you must charge more for the extra effort and risk that come with accepting pets. Pets pose a risk of damage, though typically very nil risk, to your property.
A pet fee is an amount that your guests pay to bring their pets into your home.You can charge a flat rate per pet per week or a flat rate for the first pet and an incremental amount for each additional pet.  For example 100 euro per week per week to the former, and 100 euro per week for first pet and 50 euro per week for each additional pet per week to the latter, respectively. Try also to check other rentals in your area to know what they are charging to accept pets. And when setting pet fees consider too any extra cleaning costs that your housekeeper might charge.
 In conclusion, weigh first the pros and cons when deciding whether or not to accept pets in your vacation rental.  You might be attracting renters but you could also be exposing your property to more wear and tear and the risk of damage.