"What can you tell me about dedicating sexual intercourse to one of the love gods? Would it be possible to make having sex part of a ritual to someone like Aphrodite or Eros?"
Hellenic society was complicated when it came to sex; the ancients saw sex as completely natural and--unlike many today--had no inhibitions and very few taboos when it came to straight up heterosexual sex. Anything else had societal stigma's attached to it. Nudity was generally accepted by the ancient Hellenes, although social rules had to be observed. Women rarely went completely uncovered in every day life, but displayed their bodies through their clothing. Men could cast off their clothing more readily. If either gender undressed, it was seen as irreverent to do so partly, and thus they appeared either fully clothed or naked. Partial nudity was frowned upon in almost all social settings, while full nudity was often accepted.
Ritual prostitution was a valid form of worship for Aphrodite in Cyprus, the center of her cult, in Cythera, Corinth and in Sicily. The women were called 'hierodoule' (ἱεροδούλη), temple slave, and 'made love' with paying customers. The practice was considered distinctly 'un-Hellenic' by 460 BC, but it made Corinth very wealthy, indeed. The practice seems to have lingered in converted Corinth from earlier worship of Astarte, who was brought into the pantheon as Aphrodite in Hellas. Pindar describes this exact practice beautifully in his 'Eulogies' (Fragment 122):
"Young women visited by many, servants of Peitho in rich Corinth, you who burn the tawny tears of pale frankincense, on many occasions fluttering in thought to the Uranian mother of desires, Aphrodite--To you she has granted without the possibility of refusal, O children, to have the fruit of your soft bloom plucked in lovely beds. And with necessity, everything is beautiful."
Aphrodite is the professional patron, protector and avenger of hierodoule as well as hetairai--female companions, a term used non-sexually for women, about women, but used by men to indicate a woman hired for entertainment, often leading to sex. She passes no judgement on those who enjoy the sanctity of sex and offers protection to those who practice it for money. That said, I don't know if the sexual encounter with the hierodoule were practiced inside the temple, or dedicated to the Goddess at all; it could just be a form of prostitution and a way to enrich the temple and city.
Within the Eleusinian Mysteries, there is also mention of sex--since many of the festivals have to do with fertility and childbirth. Most of those mentions take place at home, however, in the sanctity of the oikos. While this lovemaking was obviously linked to the Mysteries, I am not sure if the Gods were actively asked to witness the events. It was something that happened in the spirit of the festival, yes, but even then, the Mysteries are an old tradition. The cult itself likely has origins dating back to the Mycenean period of around 1600 to 1100 BC, and it is believed that the cult of Demeter Herself was established in 1500 BC. These proceedings were a secret, and although many people were a member of the cult, speaking of anything that happened during the rites was punishable by death.
Now for the practical: within the Hellenic religious practice, miasma describes the lingering aura of uncleanliness in regards to a person or space through which contact is made with the Gods. Miasma occurs whenever the space or person comes into contact with a pollutant--which includes bodily fluids. Mikalson in 'Ancient Greek Religion' mentions that a bath was required before entering a temple after intercourse as a form of katharmos. He, however, does not give a source, and I don't know one either. It is a reoccurring idea, though, mostly centred on the male's excretions during the activity. The Hellenic religious organization 'Labrys' echoes the sentiment, but also without sourcing. Miasma would be one of the reasons I can think of that would support abstinence in a religious setting.
There are five steps to proper, Hellenistic ritual: procession, purification, prayers and hymns, sacrifice/offerings, prayers of supplication and thanks, usually followed by a feast and/or theatre and sporting events. Personally, I don't see a way to include sex in this format. Making love in the spirit of a festival, sure, but seeing as it seems impossible to follow the proper steps and make love--not to mention the very important influence of miasma--I don't think we should include the Gods in our lovemaking. Personally, I don't ask Demeter to watch on for the Haloa--nor would I feel at all comfortable having the eyes of the Gods on me when I make love. My answer to the question would be 'no', but if you come to another conclusion, please fill in your practice as you see fit!