Good luck, you're falling in love. My advice to you is, this one is worth being careful with. You've got a lifetime to be in bed with him if you like him that much. An adventure? ok, but by the sounds of it, this adventure could last a lifetime IF you want it to. So go and meet his mum, get on with her and respect her. Tell him you think it's disrespectful to assume you can sleep together at his mum's and you'd rather save that for another time. He'll love you for it if he's worth having, and you may as well know right now whether he's worth having or not. And if you really get on that much, it's not ALL about sex. You want the relationship to stay meaningful right?