If two parents have a gap between their front teeth, would their child have a gap too?

Depends. Remember child inheriting genes from 2 parents, 4 grandparents, 16 great grandparents, etc. Add to that environmental concerns, such as digit habits, and it's quite a complex situation. However, the probability is fairly high, so expect to take your child for their 1st orthodontic check-up at age 7.
Possibly. …but not necessarily. Genetics can be quite hit or miss in any individual progeny.