Is it safe to take baths in the 3rd trimester?

Yes: It is absolutely safe to take baths. Some women labor or even deliver in a medically supervised bath (ie. Water birth). It's a great way to give yourself some "me time". Light some candles, use some relaxing lavender essential oils and enjoy.

Of course....: Sounds like a great way to relax. I'd take advantage of the opportunity now, as similar escapes with a small child, or a toddler, or a school age child, or a pre-teen, or a teenager will be few and far between, and in each case for different reasons. Enjoy this while you can, then enjoy all the joys of parenting to come. Congratulations and cheers to you....