1.Is it OK to say: They're going to celebrate their 30th
marriage (
you could omit marriage) anniversary.
2. These are the politicians who trigger off wars and civilians die. You've used the Present simple.
Is this something usual for these guys? If not it should be '... triggered off wars and many civilians died.'
(I do not know why, but I was thinking for a while that it should be: This is the politicians No. Because you're talking about
many politicians. 'This' is for singular while 'these' is for plural.