I studied Japanese for a couple of years (ahem, a while ago). I think you may be better off with simpler statements. Asking if they can guarantee that you won't be served meat seems strongly worded to me for a Japanese context.
I looked at a few sites like this one to get some ideas.
You're much more likely to be served something with seafood in it rather than with meat (although watch out for bacon, I guess). Dashi, bonito flakes, roe (fish eggs) all get used in a lot of sauces and dishes where you might not expect them.
すみません。 肉が食べられません。 Sumimasen. Niku ga taberaremasen.
Excuse me/sorry. I can't eat meat.
魚は大丈夫です。 Sakana wa daijobu desu.
Seafood is fine.
When you're actually ordering, check whether there's meat by pointing to the item and saying:
これは肉がありますか？ Kore wa niku wa arimasu ka?
Is there meat in this?
Hopefully, the server will answer something like:
肉がありません。 Niku ga arimasen.
There isn't meat.