Our Calfee tandem purchased in 2011 was built by me with FSA Gossamer triple crankset 50/39/28 chainrings with 10 speed 12-36 cassette.
Front cranks are 170mm and rear 165mm.
I have a SRAM 10 speed shifter for rear and Campy Centaur triple for front.
I have gotten good at shifting the front but still often I mess up a shift which can be hard my wife's legs. Recently the middle chainring is dropping the chain to the small chainring when pedaling on the large rear cog. Looks like the chainring maybe worn and need replacing. Sometimes I get confused which chainring I am on. I have been thinking about upgrading the drive chain for some time. Here is the proposed upgrade:

Appleman tandem crankset 170mm front, 165 mm rear. Nobody else makes this combo.

Shimano GRX 46/30 chain rings, 11 or 12 speed 11-36 cassette.
This would keep the same highest gear, but lower gear would be slightly higher. TA makes a 28T GRX chain ring that might work.
Another option would be Praxis 48/32 but we are old and really need the lower gears. I would need to change the bottom brackets for the 30mm crank spindle.

I already have a pair of Force 11 speed shifters so it would save some money to go 11 speed. I could possibly use eTap but that would cost a whole lot more and I don't mind mechanical.

I figure this is going to cost me $1500 or more. I could simply spend $100 on new chainrings for my current setup. Crankset alone is $1260. It might save a bit of weight.

I think the main benefit here is smoother shifting making for more enjoyment. The Calfee has served us well for its 14 years and I think its time to do this. Thanks for any thoughts / feedback.