Ooh, you must be feeling excited!
From a digestive pov with rats there's no need to slowly change their food over. They're opportunistic scavengers (for the most part) so very much designed to eat what there is evolutionally, which is nice and easy. If their diet has been very monotonous though, psychologically they may take a little bit of time if they're particularly wary of new foods. I would plan to change them over straight away, but you could feed 50/50 for a short while if there are problems. Even a rat who is wary of new foods won't let themselves starve though, so I wouldn't particularly worry.
Bowl feeding them for a little bit while they settle in and you assess them, their condition, and how much they're eating sounds like a good plan. I mean you could switch to scatter feeding straight away, but if they're used to nuggets also and you're changing them onto RR (good move!) then you may end up with a lot of wastage/ unbalanced diet to start with as they won't be used to the small piece size etc. So overall I think your plan sounds like a good one
Beri with all at Dandelion Soup
Pow, Nessa, Orin, Liffey, Aoife, and Petra (bundle of multis), Whimbrel, Dotterel, and Kestrel (zebra mice), Woodbine and Speedwell (gerbils), a large selection of fancy mice, and Moril (cat)