You received a lot of great suggestions...I have to say it though...Unless he is also 5, he should be old enough to entertain himself. If you have the time and energy to plan activities for your 5 year old and your bf, then God bless, but frankly I would tell him to grow up.
(On a side note, it doesn't sound to me as though you're unreasonably tired, but if you feel like your exhaustion continues to be excessive, you might check with your ob about testing your iron...many pregnant women become anemic during pregnancy which can exacerbate the normal levels of exhaustion.)