What is the best approach to getting my 5 month old kittens outside for the first time? I'm in the U.K?

with my two kittens i carried them outside with me each day for a week and spent 20 mins outside with them then they followed me in,increase bit by bit then they will start to sit by door to go out,make sure they know there names when called,or each time you feed shake biscuit box then they will come back into that.with my cats i bang the 2 foods bowls together they come in without fail