The UC rules for people who are the main carer for their children are as follows:
Child is under 1
If your child is under 1 year old, you will be placed in the ‘no work-related requirements’ group. You won’t be expected to do any activities through the jobcentre and you won’t have a work coach. You won’t be expected to look for work.
Child is aged 1
If your child is aged 1, you will be placed in the ‘work-focused interviews’ group. You won’t be expected to look for work. However, you might be asked to have interviews with a work coach about the kind of work you would like to do in the future.
Child is aged 2
If your child is aged 2, you will be placed in the ‘work preparation’ group. You won’t be expected to look for work but you might be expected to take part in activities to improve your chances of getting a job in the future.
Child is aged 3 - 12
If your child is aged between 3 and 12, you will be placed in the ‘all work-related requirements’ group. You will be expected to look for work and to be available to take up a job if one is offered to you. You won’t be expected to take a job that would mean working more than 30 hours per week and you won’t need to spend more than 30 hours per week looking for work.
As pps have pointed out, you can get 30 hours per week of free childcare for children aged 3 - 4 years old and this will enable you to return to work and meet your UC claimant commitment. You don't say what work you did previously, but you may be able to find work you can do from home.