We bought Asha a toddler bed from IKEA ... she was so tiny but was trying to climb out of the cot! It has adjustable ends so it can start with both ends up and then as they grow you can lower one end and then the other. I love it and it is low enough to the ground that the couple of times Asha has fallen out she hasn't badly hurt herself!

I would do the whole lot at once ... new room & new bed ... big boys room, big boys bed! I am sure he will be fine. He may seem unsettled for a few nights but it wont take long for him to settle. The only thing I will say is once you make the change, dont go backwards ... that is too confusing!

Good luck

Cheers