Once you get them the toddler beds, make a big deal about what big kids they are now, buy some new special sheets that they help choose, this will help to get them excited about their "new" beds.
Getting them to stay in the bed is kinda the same thing as getting them to learn to fall asleep on their own, it takes a few days.
At bedtime again talk about how great it is they now have big kid beds and that they need to stay in them and not come out. I put my son to bed that way and then stayed at the bedroom door, out of eye sight, when he got up I went in and put him back in bed and told him he needed to stay in bed. I only had to do it a few times. Next couple of nights probably the same thing, each kid is different, mine took 2 nights my friends child took 3 nights.
Remember baby gates not only keep kids out of areas but they can also keep kids in areas! You can always put up a baby gate at their door to keep them in if you don't want to
stay next to the door. This is also good if you are worried about them wandering in the night or are early morning risers.
Good luck!!