if there are 3 in your group that will be doing the park at a busy time, it would probably be cheaper to stay onsite one night.
onsite hotel guests receive unlimited ep usage.
the vip tickets are date and park related.
check out the website calendar to see what costs they are first.
then break down on how much the park ticket would cost at cosco or UT.
look and see what regular epp sell for on the date you are considering.
that will help you determine if the vip tickets are worth it to you.