I would do the toddler too. Depending on the toddler and whether they were in prior care they may have a harder time adjusting than a 12month old.
Transition needs to be daily otherwise it is just harder on the kids. If you plan to do a week of transition I would do 5 days of care. Day one: 2hrs first thing in morning. Day 2 half day leaving before lunch. Day 3 half day leaving after lunch. Day 4 stay and go right after nap. Day 5 a full day.