if you'd like to go all extra credit then maybe make little holes in the bottom of any fencing so they can get through and explore other gardens
https://www.hedgehogstreet.org/help-hedgehogs/link-your-garden/
maybe put out some food for them, they mostly enjoy meat-flavoured cat food (both wet food and biscuits)
https://www.hedgehogstreet.org/help-hedgehogs/feed-hedgehogs/
maybe even build a hedgehog house and give them a place to stay! (also building one will keep any kids you have busy for a couple hours)
https://www.hedgehogstreet.org/help-hedgehogs/hedgehog-homes/