Thats a big move and event to do at the same time ! Is he climbing out of the cot ? Does he have to go into the big bed straight away ?

I can only go off what Cait was like - at two years and two months she hated the big bed, completely freaked out in it. Tried it again a month later and she was fine. With the bed/cot change over - she used to love the garbos and I used to rattle her cot and say it was broken and the garbos were going to take it away, she was OK with that. Also, I used the side off her cot that came right off and clamped it to the side of her bed similar to a safety rail (looked OK as everything was white) and so it felt like the cot a bit too.

Don't rush it unless you have springs in your buttocks - you'll be getting up and down as much as he does :-)