OK, wait, I'm confused.
You said above that they are 320x240.
That is a non-standard format, which is why dvdlab is freaking out.
VCD is 352x240.
You can encode them in SVCD (480x480) if your player will play them, otherwise you must encode in DVD (720x480) for them to play, or halfD1 (360x240).
DVDLab will accept SVCD and allow you to author them to dvdr, but again, your player may not play them. DVDLab definitely does NOT like non-standard formats nor does it like VCD. (as Viper has noted above)
I think you're going to have to re-encode them into a format your player (and dvdlab) will accept. In this case I would recommend HalfD1, or SVCD.
Just keep the bitrate down (WAY down) and you can probably fit 3 full length movies on one dvdr, without sacrificing any quality, because it's still going to be better than VCD (1150kbps).
If you can play svcd's, dvdlab will allow you to author them to dvdr, even if it has to transcode the audio to 48khz (if your encoder will allow you to encode svcd with 48khz audio, do it!), and will put up a warning about "this is an SVCD framesize used for DVD...". Ignore it and author as normal.
If your player will ONLY play dvd, and not (S)VCD, then I suggest you encode them as dvd, with a very low bitrate (less than 2000kbps) and author 2 or 3 on the same dvdr. No point in wasting space.
Edit: Thanks Viper, and yes, you could use my guide to author a really nice multi-movie dvdr, using svcds, or low bitrate dvds.
If you need more help on getting svcds or multi-movie dvd's authored, just ask