Downing Street has previously said no unaccompanied children would be sent to the Rwandan capital.
Rwanda is making preparations to house child asylum seekers removed from the UK on a one-way ticket under Boris Johnson’s widely-criticised policy.
The Hope Hostel in the capital of Kigali is constructing a five-a-side football pitch, a basketball court and is considering purchasing outside toys for minors, it emerged on Friday.
Downing Street said no unaccompanied children would be sent to the Rwandan capital 4,000 miles away and insisted it was right to “prepare for all eventualities”.
Hostel manager Elisee Kalyango confirmed they were taking steps to prepare for children coming under the policy, adding: “We are ready to handle people from any age.”
Being built were a “mini football and basketball court which can be shifted to volleyball”, he said, and for children they were considering getting “toys” to be placed on the nearby lawn.
The manager was speaking to journalists who travelled with the Prime Minister to Rwanda, where he is attending a Commonwealth summit, as he showed them around the accommodation in a visit arranged by No 10.
The Hope was empty. Mr Kalyango said the individuals who were living there, understood to have included orphans of the Rwandan genocide and students, were housed elsewhere shortly after the Government signed the £120 million economic and migration deal in April.
Lord Dubs, who was welcomed to the UK when he fled the Nazis in Czechoslovakia under the Kindertransport scheme, said the revelation about children was “utterly unacceptable”.
The Labour peer told the PA news agency: “I think it’s utterly unacceptable. The policy of sending people to Rwanda is awful enough without adding that they are going to send children.
“I don’t know how they think they can get away with it – I think it’s deeply, deeply shocking.
“It makes it clear they don’t care who they send to Rwanda – as long as they get rid of people.”
But the Prime Minister’s official spokesman said the Government needs to prepare “facilities for all eventualities” and insisted 90% of those travelling across the English Channel in small boats are men.
“It’s right we prepare for all eventualities and you can see we have prepared properly,” he said.
“Our view is we have taken significant steps, as have the Rwandan government, and those running this site, to make sure people have everything they need here and opportunities to resettle and live their lives.”
Pressed if the Government will deport children who arrive in unauthorised trips with their parents would be deported, he said: “It will depend on those who make the journey.”
Shadow home secretary Yvette Cooper said: “For them now to include vulnerable children in their plans is sinking to a real new low. (Home Secretary) Priti Patel should be ashamed.
“The Home Office should stop this damaging plan, start targeting the criminal gangs and sort out their own asylum decision-making instead.”
Earlier, Mr Johnson admitted that Ukrainian refugees could be subject to the policy that has been stalled by legal challenges.
But the Prime Minister insisted to reporters it is “very unlikely” that asylum seekers fleeing the Russian invasion will be caught up in his widely criticised policy.
Labour said it was “disgraceful” that Mr Johnson believes it is fine to send those fleeing Vladimir Putin’s bombs to Rwanda.
Rwanda’s human rights record is high among the concerns about the £120 million economic deal, but no one-way flights for migrants have taken off yet.
The first was due to depart last week, but was grounded by legal challenges.
Despite the scheme being stalled, it also emerged that Britain has already made payments to Kigali, which has begun spending the money in preparation for receiving asylum seekers.
The Rwandan government said it had begun spending the cash to be ready in time for last week’s flight, which was cancelled at the last minute.