Wow, they do look fragile, don't they?
Really the only thing that holds aluminum with any strength at all is epoxy. CA is kind of a time bomb- it could go at any time, as aluminum doesn't have enough 'tooth' for CA to properly bond to. It looks like if the resin centres are properly glued in, the glue bond will give them (and so the whole wheels) some strength. So if you want to prepaint the centres, I would go ahead and do it. After the paint is dry, epoxy them in place by applying a line of epoxy around the back of the resin ring, maybe with a toothpick. (If you use the 5 min variety, you probably won't manage more than one wheel at a time before glue sets.) Be careful not to get the epoxy anywhere else on the aluminum, as you won't really be able to clean it afterwards. That should do it....