If they pay you with a small fee you can do a CPFP so it shouldn't be a problem because anytime you can make a transaction with the unconfirmed transaction and add an extra fee but to make sure it would confirm check it first on the blockchain explorer if it's not a series of unconfirmed transaction because if it's a series of unconfirmed transaction even you do CPFP with high fee there still a possibility the transaction will be rejected.

Or you can just wait until the receive transaction is confirmed before you spend since Electrum has coin control it shouldn't be a problem if you want to spend only confirmed transactions.