Goodness, this is an old form of bigotry you don't see around much these days.
It is absolutely disgusting to equate learning about LGBT with learning about BDSM, dogging and masturbation. The latter three things are specific sexual practices and clearly not suitable topics for children. Being LGBT isn't a sexual practice - it's an aspect of your identity. Kids know that relationships happen - you aren't hiding the existence of heterosexual couples from them in fear that it is an inappropriate sexual topic, so why do you feel differently about the LGBT community?
Ah, the instant 'bigot' accusation. 
If they're only telling them about the fact that same-sex couples exist (which they probably already know anyway), that fact doesn't indeed relate to a 'sexual practice' as far as it needs to concern them, so why ever do they need a full day or course to examine it? What are they taking the time to discuss?
As a PP said, if you tell kids that this [same sex] person is my life partner/wifet etc, they'll often just say, "Oh, OK then" - and if they say they didn't know that a woman could have a female partner or a wife, it will be easily answered with "Yes, an adult can form a partnership or marry almost any other adult, regardless of their sex". Most kids couldn't care less (possibly beyond an initial childish giggle of unfamiliarity that is quickly countered).
To most kids, it would be the same as introducing another child by saying "Lucy, this is Michelle" and then, instead of just letting Lucy take a second to say "Hi, Michelle" somehow feeling the need to have a discussion or workshop themed around the way that people can be called Lucy, Michelle, Timothy, Claire, Bradley whatever. Labouring a point that they instantly accept is just unnecessary and might make them question why you feel the need to do it.
I don't see the need to take any time to discuss 'sexual practices' with any children of this age. Yes, being LGBT (or indeed straight) is part of your identity, as with other basic, easily-graspable facts such as your name or sex, but they do not need any further details at their age of how this may be expressed between adults.
In the same way, you might say to children "This is Natalie and she's a police officer" and her job would likely also be part of her identity, but you wouldn't dream of then starting to give them child-inappropriate details of the gruesome murder that she had to attend to the previous night.