Steve, there is nothing wrong with you bathing with your son. When I was younger i would bathe with my dad, but never with my mom. Maybe you should let your wife take over bathing your daughter.

If you don't bathe with your son or if your wife doesn't bathe with your daughter then they will think that it is wrong to be naked in front of there kids when their all grown. Of course, there is a cut off point. You and your child will feel the discomfort. Possibly age 7. If you want to tell them about puberty take them aside and tell them. My dad told me about puberty on a camping trip in the woods. He showed me what i would look like when i was his age and told me about pubic hairy and masturbation. That is perfectly normal and I love my dad for that. After that we had the best relationship, although we had a good one before this. When I was 15 he told me about sex and about condoms and such. He showed me how to put one on. And your wife should do the same with your daughter.

Do what you think.

Richard