What's the ISP plan speed, and make an model of the router. Every router is different with different software, so you need to be more specific with your plan speed and router model.
A phone and a game should not take much bandwidth. But with 10 people, you may run into issues if someone is downloading a console update or game download. Despite what other on here have said, it's likely those people that are hogging bandwidth which is unfair. A phone game should not use much at all.
If you router has bandwidth allocation, you can limit everyone to a maximum amount of bandwidth, that way if they do a console or game update, they won't saturate the download with just their own bandwidth.
If not, it's best to buy a more advanced router with traffic shaping algorithms like FQ_CODEL or CAKE, which will allocate bandwidth in a more equitable manner.