I'm no expert, but...
I should think there are loads that meet your requirements. I love my CO2 pellet revolvers, but if you want to avoid anything 'fiddly' would ignore them. Due to the hassle of loading cartridges.
I let my g/children use a bb Luger PO8 replica, with 2 17 shot bb stick magazines. Plenty of other replicas available, cheap enough.
One thing I have learnt - and I have pellet rifles from the '50's to now - is make sure you have an absorbent backstop for steel bb's.
Webley Mk3 x2, Falcon & Junior rifles, HW35x2, AirSporter x2, Gold Star, Meteors x2, Diana 25. SMK B19, Webley Senior, Premier, Hurricane x 2, Tempest, Dan Wesson 8", Crosman 3576, Legends PO8.