sv 3-1 permutations with restrictions [2 people in a back seat of 3]

It covers 2 similar problems:
1) A family of 5 in a 5 seat car where 2 children must ride in back
2) 6 friends on a ride with 2 benches holding 3 people each. 2 friends want to always be in back.
-- These problems also look at what to with something that seems like 2 people permutating over 3 seats (a situation where r seems bigger than n)