Hi @Sonny.Ade,
It depends on what you’re looking for. The two Sonos Ones and Sub configuration will give you better bass, while the Sonos Fives will give you a better soundstage and sound coverage for the Dinning room. In this scenario, it’ll be up to you to decide what is worth more, but in my opinion the Fives will give the richer sound experience. If you are set on getting a Sub, perhaps a Sonos Sub Mini will suit your needs better in this case.
I do have a question regarding your Living room setup however. You mention having two Play:1s as front speakers and 2 Sonos Ones as rear speakers however, unless you mean the general placement of the speakers, this isn’t possible as a Sonos setup. For speakers to be regarded as front or rear, they must be part of a Home Theater setup, which requires a soundbar and optional surrounds and sub. Is your living room setup connected to your TV in any way or are the front and rear speakers you mentioned only relevant to your listening position?
If your living room setup is just the pair of Play:1s and pair of Sonos Ones grouped together, then grouping the additional dining room speakers would not create any sync issues. If it is a Home Theater setup with a soundbar, then you will experience sync issues when grouping the dining room speakers.
I hope this information helps!