I think you'd be surprised how successful you would be as a trio! Aside from experience points, most things in Abyssea these days are done with anywhere from one to four people. Rarely do you see more than four doing anything other than exp.
Regarding setup, your THF should have pretty decent evasion, so if you can grab one evasion atma I bet your evasion would go through the roof. If not, you can probably just go full DD atmas to kill faster. Since you should have 2k HP or more, it's rare that you'll go down quickly. If your WHM has Minikin atma and a couple other decent ones, they should never run out of MP, so as long as you don't die in a matter of seconds they should be able to drop a Cure V and get your HP back up. Also if they have good enfeebling skill, or sub SCH for Light Arts, they should be able to land a nice Slow & Paralyze to help you tank.
As far as what to kill, let me see... Coin of Voyage drops from Carabosse, Hadhayosh, Karkinos, Sedna, and Ketea. Of those, I'd say Sedna is probably the easiest. You only need two key items to pop it. Make sure WHM uses Barwatera, and the fight is a joke. Alternately, Carabosse is farmed regularly for her gems to make empyrean weapons, so if you can find someone farming Carabosse and tag along with them you could probably get coins pretty easily that way. They always want THFs to improve the drop rate for gems.
As for Jewels of Voyage, they drop from Durinn, Sedna, Briarius, Hadhayosh, and Karkinos. Looks like Sedna is your best bet again. Briarius is the alternative here, as he's also farmed for empyrean weapons so you may be able to find a group doing him.
Honestly, you could probably get these simply by showing up at Carabosse / Briarius camps and seeing if there's a group already there who doesn't want their coins/jewels. In fact, Sedna drops items for empyrean weapon too, but it's just that nobody ever farms that one lol... so you'll probably have better luck farming it yourself.
Oh, one last warning: If you do decide to go for Sedna, which I think is your best bet, be careful on Hrosshvalur. It randomly loses hate and starts sniping mages. So make sure your WHM keeps Barwatera up (on the BLM as well) and probably Stoneskin too. It does almost no damage, but it knocks you back really far and is annoying. The other NM to pop Sedna, Iku-Turso, is a fairly typical sea monk but Maelstrom can hit pretty hard, so again, keep that Barwatera up. Also, Iku-Turso gains a silence aura after Maelstrom, so make sure the mages aren't standing near it.
____________________________Pergatory (Asura, Kupo LS) WHM99 ~ SMN99 ~ DRK99 "If you want to know me, look inside your heart." -Lao Tzu