Erm, no-one has actually reached Slateport yet... a couple are on the boat there but most are still either heading to Dewford, or are on Dewford itself. For this reason, I'd prefer it if you started on Dewford. You can start with the team you mentioned and the first badge already won. Since you already have Aron, all you would have to do on Dewford is challenge Brawly.
I think this would work better, as otherwise you would make one post and then be waiting for all of the current RPers ti catch up :/