Its not the belt that lets go usually its the tensioner or idler pulley so definately change both. To make life easier get a timing kit which has a flat bar to lock into the end of the cams and a timing pin to find TDC, you screw the pin through the block and it locates onto the crank.
Water pump is worth changing also along with Aux belt. One thing to note is that the VVT is very sensitive to change, if you do not loosen the cam pulleys when timing up the engine you will get a MIL light on the dash. this is because the belt will have stretched and the VVT will throw up a VVT advanced fault. Good luck
p.s It worth getting a cam cover gasket too as you have to remove this and they tend to leak if not changed. DO NOT use the flat bar inserted in the end of the cams of the locking pin to hold them into position when loosening the cam pulleys, use a 19mm spanner on the flats cast into the cams otherwise you will shear the ears off the end of the cams.