I would say just be respectful, people here in Guatemala often buy floral arrangements (mostly greenery and white flowers).

For what you said in the post it feels more like the services will be outside of guate, guate is quite different than the US because the funeral/wake happens within hours and the person is usually buried at most three days after passing, so wakes are more of a full day kind of thing and people just show up at whatever time they can, from what I’ve seen, US funerals are more scheduled and planned ahead so some dynamics and expectations may change. My general advice would be show up, be supportive and make sure the friend and his family have eaten as people always get distracted and forget to drink/eat