Thanks, however I seem to be unable to do this via the GUI. Even when selecting outputs manually it only shows those that have confirmations, I cannot choose an output that is unconfirmed.

So it seems CPFP is impossible via the GUI.

I haven't seen what happens if I try to do it via 'sendtoaddress' RPC but I'm pretty sure it will just say "insufficient balance" if I try to include the whole balance of confirmed and unconfirmed UTXO.

I believe creating a rawtransaction is the only way to do CPFP in Bitcoin Core and that's why I've implemented it this way. Please let me know if I'm wrong :-)