They can full attack, although at -2 penalty...
albeit your DEX is also penalized by 4, i.e. -2 AC and CMD except for Grapple, so it cancels out.
(it is usually easier to break/reverse a grapple than establish a new one from scratch, because the grappler's own CMD is also penalized)
The only restriction is for actions requiring two hands, so IF the Slam natural attacks are supposed to be it's hands,
that could be barred (as 2WF'ing with left and right hands would be), but a creature with Bite/Gore/Wing/Wing/Slam/Tail could use all of them.