What to do with this Golem?
TMs? Power it up to 30? Power it up to 31.5 (for Moltres)? Nothing?
I currently have 2 Golems with RT/SE. One is 98% level 34.5 and one is 80% (15 attack) at level 31.5. I have one Ttar B/SE at level 31. I also have a handful of Rhydons with all move combinations. Geodudes are rare for me and I only have 35 candies.

Answers
Taking it to 30 would be nice for Moltres and Zapados if he got rick moves. On the bright side 1 of each TM guarantees you rock moves. On the downside we don't know when we will need a ton of Golems again after the next 10 days. If you are losing legendaries due to bad teammates you it might not be a bad choice but it's sad as hell that you would have to spend to earn them a mon they don't deserve in the least. Tough call man but that's all on you.
If I told you I'd sell you a Moltres for 20K dust, 20ish Golem candies and two TMs would you do it? Just wondering.
If they are failing against Moltres, Zapados is going to be a nightmare.
Yes, Zapdos is a real concern for me. I've only been able to attempt 2 moltres raids (none caught). My raids groups are all over the board. I live in a small town where at level 34 I'm easily a top 10 player. Sometimes we have 15+ in a raid. Sometimes we struggle to get 5. My work schedule basically gets me one shot at Moltres per day.
I think I'm talking myself into doing it!
I wouldn't. I don't want to sound like an IV snob but you will find better. Losing a close one sucks but the odds that you will fail another raid that you could have won by swapping 1 poke is extremely low. I would start walking Geo candies though. By far the best buddy now that rare candies are a thing!
not worth the effort, just need to make sure everyone knows what they are doing before you go in.
When I raid and there are people <lvl 30 i ask 'do you know what to use?'
Incidentally did the lapras have water moves? if they were low level they might not have had a lot of choices (egg is super dumb though),
But it's funny when you see level 24 players with a fist full of legendary mons and tyrantars and no vapes.
leave your golem for second line against Raikou