Tipp: If you are planing to grow beyond your 31 relays I recommend you preemptively generate the keys for your upcoming relays so you don't have to touch all other relays everytime you add a single relay (to the MyFamily line).
How do you pregenerate keys? Id be interested as Im spinning up quite a few soon
create a folder per tor instance:
mkdir future-relay1 future-relay2 ...
then invoke tor manually (this will just generate keys and exit after that):
tor --PublishServerDescriptor 0 --orport auto --list-fingerprint --datadirectory future-relay1 --Log "err stdout"
tor --PublishServerDescriptor 0 --orport auto --list-fingerprint --datadirectory future-relay2 --Log "err stdout"
...
In these folders you will then find the fingerprint that you can use in MyFamily, so you don't have to touch your existing relays anymore once you actually use these generated keys on new relays.
Make sure you take care of filesystem permissions when using these keys on the actual relay.