I run 8 speed trigger shifter on my mountain bike with a 7 speed cassette. Some people just ignore the slight shifting differences, but I sand down the plastic spacers to match the 8 speed cassette.

As for the front, you probably could try a road triple. My wife's road bike is running a Tiagra 4503 or 4603 that works with her 46-39-30 triple. She was using ST2300 but is now using Claris shifters. I'm not sure how it will work with a 24t granny, but was happy that it shifts to th 46t without any issues. Some road front derailleurs are not happy with a smaller large chainring. I have tried an older 7703 and it doesn't work as well.

John