Assuming everyone's located near-ish, Whinlatter forest nr Keswick has a chilled but fun easier loop along with a harder trail option, and there's a good bike hire spot there along with a cafe. Also within easy drive radius there's a paintball spot, which I once went to on a stag, and go-karting. If you're all further north, or like your biking then the Edinburgh trails are DEFO better.