Moving from Canon T2i to Mirrorless - Recommendations and Advice?

I have recently "gifted" my Canon T2i to my daughter and son-in-law to take pictures (for me) of their 1 year old son. In looking to replace, I have considered the Canon T6s with 18-135 STM lens but have received several recommendations to move to mirrorless. My most used Canon lens was the 18-135 STM. I am told that the newer mirrorless cameras are every bit as good as the older "consumer/prosumer" DSLR's. Given my age (turning 60) and travel to see my grandchildren, size is becoming a concern.

I will admit somewhat of an emotional struggle moving away from the DSLR - I have used an SLR for almost 35 years. One of my concerns is the ability to take motion shots of my grandchildren - or animals in nature. I am told tracking is not as good. Comments/thoughts?

I have been advised by 2 different camera stores to consider the Olympus M10 or M10 Mark II. They advise that the Pany G7 is too big and not as good with stills (although grip/ergonomics feels good), the Sony a6000 is not cost effective if I want the longer range walk-around lens, and that the Canon M3 is just not there yet in comparative IQ and lens choice.

I know this forum is "biased" towards mirrorless///4/3 cameras, but you also know them the best. Is the Oly M10 or M10 Mark II the way to go? How does the Oly 14-150 lens stack-up? Is there a big difference (other than price) in the M10 and the M10 MarkII? What other accessories should I consider?

Other than the typical B&H, Adorama, local store, is there a particularly good source for "reasonably priced" equipment, its been five years since I last bought.

I am planning a trip to Costa Rica at the end of the month, so I need to make a decision soon and can not wait on the next round of new introductions.

I know I have asked a lot, but value your advice as the experts in this arena.

Thanks.