Yes, with Neosine and Mantusil you can give your child Mucosolvan. These preparations do not interact with each other.

The last dose of Mucosolvan should be given no later than 4 hours before bedtime.

If, despite the addition of Mucosolvan, you do not notice any improvement after about 2-3 days, you should consult your pediatrician again. You may need to administer steroid anti-inflammatory drugs in the form of inhalation, which are only available on prescription.

Here you can compare the prices of Mucosolvan in online pharmacies and place your order with home delivery or pharmacy pickup:

https://www.gdziepolek.pl/produkty/50558/mucosolvan-syrop/apteki

In cities such as Warsaw, Wrocław, Katowice, Kraków, Lublin, Gdańsk, Łódź, Szczecin, Białystok, Poznań and Chorzów, products can be ordered with instant delivery in as little as 1 hour thanks to the Wolt Drive service.
Check if the service is available in your location:

https://www.gdziepolek.pl/koszyk/szybka-dostawa?src=zf

I'm attaching a link to a helpful post:

https://www.gdziepolek.pl/artykuly/kaszel-suchy-i-mokry-jak-go-leczyc