Maybe the Si5351 would do the trick (see here). It's easier to calculate and generate stepped integer frequencies instead of smoother fractional ones; though as you have a small frequency range you may be able to pre calculate more frequency steps to smooth out speed changes.
A subset of integer frequencies in the 12MHz +- 30% generated by the Si5351
8.0078, 8.0729, 8.1055, 8.2031, 8.3008, 8.3333, 8.3984, 8.4635,
8.4961, 8.5937, 8.6914, 8.7240, 8.7891, 8.8542, 8.9844, 9.1146,
9.1797, 9.2448, 9.3750, 9.5052, 9.5703, 9.6354, 9.7656, 9.8958,
9.9609, 10.0260, 10.1562, 10.2865, 10.3516, 10.4167, 10.5469, 10.6771,
10.7422, 10.8073, 10.9375, 11.0677, 11.1328, 11.1979, 11.3281, 11.4583,
11.5234, 11.5885, 11.7187, 11.9141, 11.9792, 12.1094, 12.2396, 12.3047,
12.5000, 12.6953, 12.7604, 12.8906, 13.0208, 13.0859, 13.2812, 13.4766,
13.5417, 13.6719, 13.8021, 13.8672, 14.0625, 14.2578, 14.3229, 14.4531,
14.5833, 14.6484, 14.8437, 15.0391, 15.1042, 15.2344, 15.3646, 15.4297,
15.6250, 15.8203, 15.8854, 16.0156, 16.1458, 16.2109, 16.4062, 16.6016,