Toddler travel

We are planning a trip to London in a couple of days. This will be your first international flight and I am trying to figure out all the ways we can keep you occupied on a long flight. What we may need to take with, etc.

1. Car seat - take on the plane or check? not sure if we can gate check
2. Stroller - can we gate check this? I don't really want to check it as luggage.
3. dvd player/laptop - may bring both. Our laptop goes everywhere with us.
4. Passport - luckily, we have this from our last planned trip that you didn't get to come with on
5. Busy bag - finger puppet, books, new dvd (what else is a good toy?)

Our flight from Seattle to London is a late evening flight so we are hoping you will sleep for a good portion of the flight. If not, everyone on the plane will be tired.

I am excited to go, but nervous about traveling with a 2 almost 3 year old.