Hi J.,
I don't know what to say abt them being so close to Christmas except that half birthdays seem to be a good idea. Regarding the birthdays being so close together, though...my mom had the same problem. My brother and I are 363 days apart, and we had (at least early on) the same pool of friends. So we shared parties and alternated picking themes (I endured cowboys, and he endured barbie...well you get the picture). One problem you are going to run into unless you have the perfect party house, is actually having room for a kids birthday party in the winter once you start inviting their friends and not just family. We struggle with this for my 3 y/o (soon to be 4) who has a Feb birthday and her 1st birthday party was literally snowed out. To avoid a few mistakes I have made - set times, have an agenda and activities (Oriental Trading Co has some cheap cool crafts for almost any theme), and hustle the kids out after "their time is up," and feed the parents adult food <g>. This year we had a Tinkerbell Fairy Party and strung white lights around the living and dining room, made fairy wands, and had the kids play in the Tumblebus for an hour. My other daughter (4) had a Royal Tea and made sand art crowns, played toss the poison apple, and dress-up (boys too), and had tea with royal wands (pretzel sticks in white chocolate and sprinkles), tea sandwiches that the girls made themselves, strawberry lemonade, and fruit salad in plastic wine glasses. Have fun with whatever you plan.
S.