Current Chase Sapphire Preferred Cardholder, Considering Going to Reserve - What Should I Know?

I'm sure this question has been asked a lot. I looked around through the search function but I have some questions that I couldn't get answers to.

So, as the title says, my wife and I are Sapphire Preferred cardholders for about 2yrs. We are considering upgrading to the Reserve card.

My questions:

• We are specifically very interested in airport lounge access. How's everyone's experience been with Priority Pass membership? Is it easy to get in to most lounges? Anything else I should know?
• We have two kids who we travel with - are they able to enter Priority Pass Lounges with us?
• Should I ask for bonus points for making the jump over? Is that reasonable?
• For the $300 annual travel credit - is that only for travel booked through Chase? Or will any travel purchase qualify?

Thanks in advance!