You won't harm your bandsaw cutting candles with it. However, you will have one heck of a mess because the friction generates heat which melts the wax which in turn thoroughly coats the blade, wheels, blade guides, cast iron table, etc. If you go this route DO NOT run your dust collection while doing so, you do not want wax permanently clogging your DC filters.
The suggestion of a hot knife -- or even using string or very narrow wire wrapped around the candle in a sawing motion (it might help to create a scored recess for the string/wire to rest in) with the candle restrained -- is really the preferred method for shortening a candle. A hot knife (don't use a good knife for this since the heat will likely oxidize and discolor the knife) will not chip or tear the wax and will leave just a small amount of 'bloom' around the edge that can be easily trimmed off afterwards. Although a dull knife (when heated) will cut the wax was just fine, you will nonetheless want a knife that is actually sharp enough to cut the wick.
Afterwards, if your cuts weren't perfect 90deg cuts, a hot aluminum pan (or even a frying pan) can be used to flatten and adjust/correct any imperfections. The pan and knife are much easier to clean up after than will your bandsaw. Power tools aren't the most approrpriate option for cutting really soft (and gooey) materials -- hand tools do a far better job.
Or, you can simply make your own custom candles. It is an amazingly simple craft and does not require a significant outlay to get started if you ever have any interest in such. Ultra-fine glitter and clear gel wax make a very nice single-use candle for weddings (BTDT for my sister). All you need is a thermometer, melting pot (wax goes in this pot), boiling pot (your regular pots are fine for this -- just water), candle mold and wax plus approprate wick (zinc core for gel wax). If you want dies or scents then those are simple customizations as well and are readily available. It's a great two-person job (hint, hint) one preparing and the other monitoring temperatures (each wax has a target range for pouring, and you don't ever want to reach the wax's ignition temperature), unless you are really good at keeping track of both (I get distracted too easily).
If you want really simple to make DIY candles that require zero investment and nearly zero time to create, you can purchase colored Beeswax sheets (some kits even include the wicking, otherwise purchase some wick) and roll your own candle to any height and diameter you wish. No molds, melting or boiling pots, nor time spent waiting for wax to melt followed by cleanup -- cut the sheet to size, insert wick, roll and you're done!
I haven't made any candles in a few years, but it is alot of fun. I still have tons of clear gel wax (was cheaper to buy 25-30lb carton wholesale than a 1lb tub retail)!
HTH -- and Congratulations on the upcoming marriage!
