Speaking as a future bridesmaid, I would suggest waiting until you have at least some of the details figured out. My friend asked a few girls right away, ie, I'm engaged! Be my bridesmaid! and then ended up wanting a smaller wedding. It all worked out in the end, but it was awkward for awhile.
Also, this may be unrealistic, and again, I'm speaking from a bridesmaid pov, not as a bride, but ideally, you'll be discussing your life and your wedding with your best friends anyway so they'll already be planning on attending, etc before you decide on your bridal party.
How about a specific drink gift? For example, if your boyfriend likes Irish coffee, get him some coffee, cream, irish coffee glasses, and the money to buy some Baileys! Or if he likes cocktails, get him some martini glasses, a shaker and the mixers, then give him some money to buy the required alcohol. There are so many fun drinks that you usually don't have the right ingredients to make, so make sure he's stocked with EVERYTHING for at least one drink. Including glassware. If you need more ideas about specific drinks let me know. As for the housewarming... are you looking for something practical (does he NEED a lot of stuff) or something more fun?
I also think that these are really awesome, but I want to share my experience as warning. I melted crayons in a bowl in the microwave, then poured into molds. then it took FOREVER to clean the bowl. So I think that using disposable molds is a great idea. If anyone has experience with using NOT disposable muffin tins etc. Please share!
The greatest thing about having your reception in your new home is that your wedding budget and your house decorating budget can be one and the same! (at least partially) Instead of spending money decorating a rented hall for a one time event, spend money decorating your house. So instead of buying expensive flowers that will die, spend some money on landscaping your yard, or buying potted houseplants. for example.