do you have a small (2 gallon or so) cooler? If you do, you can do a mini-mash with some pilsner, and use the biscuit and vienna malt, and then use pilsner dme to top up to your gravity. If I were to do this, my rough guess of a recipe would be:
4.50 lbs Pilsner DME
1.00 lb Cane Sugar (or character sugar)
0.50 lb Biscuit Malt
0.50 lb Vienna Malt
4.00 lb Pilsner Malt
Mash in (2.25 gallons) at about 152-153, and hold it for 45-60 minutes, drain off, add a couple gallons more water at 170 to sparge.
You should have about 3.5 gallons of wort at this point in time. Take a sample of your mixed (1st and 2nd) runnings and cool it down to take a gravity sample. At this time, add the water to bring it up to your standard boil volume.
So, I am just throwing this number out there. you have 3.5 gallons of beer at 1.040.
You want 5 gallons of beer at 1.064
3.5 X 40 = 140 points of gravity
5 X 64 = 320 points of gravity
so you need 320-140 = 180 points from extract.
IIRC, DME provides 42 p/lb/g, so you need 180/42 = 4lb 5oz of DME.
There is your basic partial mash, and you can use mashable grains, such as vienna or aromatic malt, and its a good step towards all-grain.