Life is also about loss and sorrow can bring us down if we dwell on it, I'm thankful for the wonderful years we had together and the living legacy I have through our now adult two children. Our daughter looks so much like Daeng and its haunting but in a good way as a reminder of her.
If I may give some advice, book a Sleeper compartment on the Bangkok to Chiang Mai journey very well ahead of your trip, and book a weeks accommodation in Chiang Mai (not during the burning season when smoke lies low and dense).
While in Bangkok (Krungthep in Thai) visit Wat Po Temple complex and avail yourself of an authentic Thai massage, believe me you'll float on air afterwards.
Check out the "Jim Thompson House" in Bangkok, look it up on the internet be amazed.
Beware of the Bangkok Taxi Mafia avoid them like the plague, download the Grab app in Bangkok and wherever else you go.
When you arrive in Suvarnabhumi (pronounced Suwarnaboom) airport in Bangkok take the lift down to the BTS (Train station) and do your currency exchange in the aisle leading to the platform.
Always ask the price of anything before you buy or pay, and bargain the Thais expect it; try for around 10% of the price off.
Tipping, dont go overboard, between 50 and 100 Thai baht is more than enough, but only in Eateries /Restaurants and your Hotel cleaning lady, dont tip everyone everywhere you go.
Learn some basic Thai, "Sawadee Krap" (greeting) etc and NEVER Wai (the hands together bowing thing) which will make you look like a real Clown. You only Wai to a Buddhist Monk (displays respect which the Thais will appreciate) and the King or his Mother if on the rare chance you see them in person.
NEVER get involved in a political discussion or about the Thai Royal family, its their country and none of our business.
Thai people love "Sanuk" meaning fun, always smile in every situation and make light of any difficulty with "Kortot" meaning "Im sorry", but never say it to a Woman (Yep its a male dominated culture and if you dont play your part then dont expect respect from anyone).
TAT.... This is Thailand.
Whenever there's a hint of difficulty say "Mai Pen Rai" which means "it doesnt matter everythings OK".
So much preparation to do but its all enjoyable and will enrich your experience.
I am sorry about your Wife and your loss. Nice that you and your adult daughter speak fluent Thai and that you have Thai family there to stay with. I will take your advice and only stay in Bangkok for a lil bit, me and the Wife are not much of city people and we are fortunate to live In rural Oregon. When we get to go we are going to go to the small rural areas of Thailand first and check out Bangkok and Pattaya, I will have to behave myself and not get in trouble with those beautiful Thai women, LOL. We have a small Donut shop in the bigger city North of us and the Thai owners are always nice to us there and give us extra Donuts all the time. The Thai woman that runs the shop is Beautiful and she has a cute Thai accent. We look forward to going to Thailand and we are going to have to wait a bit till we can go, but it is on our goal list. We have Family in New South Wales Australia that we want to stay with for a bit and are wanting to check out the area as well. From what I have seen the beaches there are nice clear Ocean, but I doubt I will get in the water I don't want to be Shark bait ! I have been told that Australia has quite a bit of Slavic people there and many of them are opal miners, I myself am half Slavic on my Fathers side, but I am an American Citizen born here. I have seen that New Zealand is Beautiful as well and we want to check that out too, maybe we can.
