my ds just turned 3. He has a zillion diggers and is always delighted with more!
He loves anything crafty and actually wanted aquabeads but we didn't get them cos his little sis would eat them! I have avoided moon sand for the same reasons as you although it does look fun.
He got the play doh hairdresser which he loves
Swingball
Goalposts
For Christmas he got an Orchard Toys giant tractor floor puzzle- he loves that and you can get a digger one too.