It actually both… Call now and explain your situation. Having a situation can work in your favor. If their lacs your chances will be better then like Berkeley since they don’t care what other offers you have…
If they said they have maxed out in merit ask about housing stipend… Some schools will help with housing if you ask nicely… You don’t care where the money is coming from…
With some schools you can use the higher amounts as leverage and just say “My son really wants to go here but we need some help, since X school gave us this”.
Just always be nice and not demanding