Engineer is considered combat arms and unless things have changes, you cant' do branch detail to Infantry from Engineer.
Regardless what happens, you still have several years to make the decision, not need to make the decision now.
As for you family's concern, altough family is important, when you become an adult you have to make certain decisions for yourself. Simple as that. Does your family members do everythng you want them to do?
As for going to combat, you don't control that. We are coming out of Iraq. We are supposed to "leave" Afghanistan by 2014. So as a possible member fo class of 2016, plus at least 6 months for basic training, unless there is a big war going on in 2017, you won't see combat. It's a big shift as since 2002, combat and deployments have been a regular routine for the Army. Who knows what the world situation will be 2017.
When I was in the active duty for 7+ years, no combat, few training deployments. I leave active duty join and the National Guard, I ended up in Iraq for a year.
