Although ‘Breaths’ are currently discouraged for by-stander Adult CPR, the paediatric patient in cardiac arrest is likely to be known by the rescuer, who will also be aware of the unlikely presence of any COVID symptoms beforehand. As children suffer cardiac arrest secondary to respiratory issues, CPR (including breaths) should be delivered.

Further info from Resus UK and AHA websites

https://www.resus.org.uk/covid-19-resources/covid-19-resources-general-public/resuscitation-council-uk-statement-covid-19 

https://cpr.heart.org/-/media/cpr-files/resources/covid-19-resources-for-cpr-training/english/kj1424_peds_covid19_and_cpr_200408_ac.pdf?la=en