The British Nationality Act 1981 is the counterpart in English law to the Austrian Staatsbürgerschaftsgesetz 1985. The two laws need to be viewed in concert when naturalising as an Austrian and in particular with regard to renunciation of British citizenship. When I naturalised with my son, my case officer was unaware of the fact that a minor was unable to renounce their citizenship, so I ended up also having to appeal to the discretion of the Secretary of State to allow a renunciation for my son. When this was refused, the case officer was satisfied that I had tried everything in my power to renounce my son’s citizenship.
Since families are likely to be in a similar position, if they are naturalising with children, and make, like myself have their reasons for wanting their children to also take Austrian citizenship with them (in my case, I argued that in light that my son would have to be resident in the UK in order to ever vote or to be able to pass on his citizenship only held by descent through me, and therefore that his not taking Austrian citizenship with me at the time I applied would cause unnecessary disadvantage to him as he grows up, I therefore had his application added to mine).
The important parts of the British Nationality Act 1981 to be aware of in this regard (and to furnish to your case officer once you have a Zusicherungsbescheid) are:
Part I: Section 1 (acquisition by birth or adoption) or Section 2 (in the case of the child having been born outside the UK and being British from birth by descent). Section 12 (renunciation) stipulates the conditions under which a person may renounce their British citizenship. In the case of a minor, unable to renounce, it is advisable to check whether Austrian citizenship is granted contingent on the minor reaching majority (e.g. say child A naturalises at 14, and cannot therefore renounce their British citizen by dint of being a minor, but their file for naturalisation remains open until they are an adult (ie. 18 unless already married or in a civil partnership prior to the age of 18)), at which point they then would have to renounce their British citizenship.
Suggestion: ask your case officer about the possibility to sign a declaration that you understand that renunciation from British citizenship is not possible until the age of 18 and that you would request citizenship is awarded (verliehen) contingent on having to renounce British citizenship upon reaching majority.
In the case that your child(ren) is/are substantially below the age of majority, explain that the British Nationality Act 1981 does not allow renunciation by minors, and therefore a lack of intent to renounce cannot be proven to exist, and renunciation is not possible at the child(ren)’s age. Already at the Infotermin or Antragstermin ask the case officer about how long the file is kept open for in the case of a minor unable to renounce. If the duration for holding the file open means that the file is shut before the child(ren) has/have reached adulthood, ask them to confirm whether the child will therefore not be required to renounce citizenship upon reaching the age of 18 (or upon marriage/entry into a civil partnership, where that happens before the age of 18).
In relation to the awarding of Austrian citizenship, Article 20 para. 3 no. 2 StBG is important:
(3) Die Staatsbürgerschaft, deren Verleihung zugesichert wurde, ist zu verleihen, sobald der Fremde
2. nachweist, daß ihm die für das Ausscheiden aus seinem bisherigen Staatsverband erforderlichen Handlungen nicht möglich oder nicht zumutbar waren.