use strategies that they already know how to access. Ie. how do they get a place to relax/chill out now? do they need a place to pace? are there activities that you use to help when out in a restaurant (coloring, looking at books, etc)? so give them the same tools that they already use.

Do you need to take breaks on the car ride? Plan a couple fun stops.

Is the extended family understanding and accepting? If not, start educating them now. Ask for things they may need like a chill-out space with no breakables?

Always have an exit plan if it turns bad. That way you are not scrambling and you can be cool and collected for your kids.

Music . Calm chill axing music . Music brings people together . In your situation ask the talker which is best . You'll probably know what kind of music your 6 year old like . , don't leave out the 10 yr old tho . Sit talk to them about this . Tell em ok kids we going to make this travel special and easy for all of us . Any ideas for music etc . I find it the kids guide you along . They will appreciate u ask them and guide u so don't fret about it . You might find travel go smoother than you think . Good luck x