I do agree with SW11er but if you have a service that people actually need then it can work, but the price has to be right and or worth the extra for the service. I'd say that if your main business is a kids barbers then as long as the price works (my son loves to go to the men's traditional barbers and it's £12 a haircut) and people are going there for that then you also would do well from the other things you sell if the products are aimed at your customers. I have a small kids brand and I find that when people collaborate on pop ups it works. The combined social media advertising always helps as each brand/product brings their customers and the combined reach can go further. It's not only good for revenue but it's helpful to bringing constant customers with the changing pop ups. There are loads of local small brands that would fit with yours and it wold mean you don;t need to spend as much on stock to fill the shop, at first at least with all the other set up costs. I don't know how big the space is, but could you also potentially hold workshops to utilise the space and keep people coming in?