You can use a deep cycle battery for starting, there is no need to utilise a second type. The initial amps necessary for starting your generator, is quite small in relation to what is available from your LQ batteries. There are many types of deep cycle batteries that are available, wet cell, gel etc. The common RV/marine types sold at auto parts stores are adequate, but if you are going to be totally dependent on their performance, a true marine battery will offer the best performance.

If properly maintained, wet cell marine batteries can usually be recharged up to 400 times at about 70 - 80% of their capacity. Their plates are extra heavily constructed, so as not to be damaged by vibrations within a rough environment. If you anticipate heavy loads and long drawing cycles, I would recommend a true marine battery available at any marina. If your needs are similar to what you experience now, the marine/RV variants work well at a much less expensive purchase price.

Purchase your batteries locally and look for the best warranties. Batteries are sold like mattresses, with somewhat set prices. Shop for the best pricing, and argue that the purchase of two is worth a discount. Batteries are like trailers, there is no BEST battery that suits everyone's needs.

Enjoy your trip, it sounds like an event to be remembered for a life time.