We have little toilets that most children can get onto themselves, definitely the vast majority of 3 year olds could. Toileting is assisted by staff, though in my centre, children are encouraged to try to wipe after a poo themselves, my staff will stand there and give the child instruction in how to do it then finish the job for them. We are getting children ready for school when no one will be on hand to do the wiping. We also have low hand basins and soap, etc because children are taught to wash hands regularly throughout the day.
Children are also reminded at regular times to go to the toilet - before mtea, during moring play, before going to bed, when getting up, etc - even though they aren't having accidents at home, they often do at the cnetre because they are just so busy playing with others and all the new stuff that they forget.

If you have concerns, please talk to your child's teacher, they will be more than willing to help and should take your child to show them the toilets etc when you arrrive for your first day.