First time travel to Thailand, any ideas for a 10 day trip with family (all adults)

It's our first time travelling to Thailand (frequent travellers, but just haven't ticked Thailand off yet), we are both in our 30's and this time travelling with both our parents.

Travel dates are around end of November for around 10 days, coming from Australia and East Asian background.

Looking at flying in and out of Bangkok, then spend some time in Chiang Mai, and maybe Phuket(?). I'd like some advice on places to visit, time to spend at city and roughly how much spending money we would need?

Also some other questions we have:

• Is Apple Pay accepted?
• Is it easy to withdraw cash from ATM's etc.?
• What is the best way to travel between major cities (Bangkok to Chiang Mai etc.)?
• Any restaurant or street food recommendations?

Lastly, we are more of a off the beaten path travellers, we don't really care about photo's for the gram, we just want to experience what Thailand has to offer and make sure our parents have a great time too.

Thank you everyone :)