Hi Firko! Welcome to the forum!
Just be aware that mud tyres are not the best choice for sand driving as they tend to dig holes very quickly, and before you know it you be bogged down to the chassis! Most of the guys I regularly go fishing with to Fraser just have highway tyres on their vehicles with a few opting for A/T's.
Maybe an A/T tyre might be best suited for your purposes? There are many A/T's available that will fit and most likely do what you want from them, but only 2 of them are rated as light truck A/T's in LT265/60R18 size. These are the BF Goodrich All Terrain T/A K02 and the Bridgestone Dueler A/T D697.
If you end up staying with 19" rims there are no LT tyres available, but the Cooper Zeon LTZ, Goodyear Duratrac and Hankook RTF10 seem to be popular.
http://www.aulro.com/afvb/d3-d4-rrs/...5-55-19-a.html
Hope this helps. Cheers!