Hope not sounding redundant, but IMO I think Oceania is an excellent choice.
We too used others RCCL, Celebrity etc when our daughters were children (we are now in our sixties), then went on to Oceania. Bermuda is beautiful , it should still be warm
in September. The two ports are nice to have. Only caveat in September is that it is still hurricane season. Yes we have sailed at that time but kept our fingers crossed.
Definately try LaReserve dining experience, so special.
wishing you safe travels !